AQA GCSE Science: P1b 5.1 How dangerous is a ray of light? AQA Specification Link • Electromagnetic radiation travels as waves and moves energy from one place to another. • All types of electromagnetic waves travel at the same speed through a vacuum (space). • The electromagnetic spectrum is continuous, but the wavelengths within it can be grouped into types of increasing wavelength and decreasing frequency: gamma rays, X-rays, ultraviolet rays, visible light, infra-red rays, microwaves and radio waves. • Electromagnetic waves obey the wave formula: wave speed = frequency x wavelength (metres/second, m/s) (hertz, Hz) (metre, m) Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Special needs • The names of the regions of Lesson structure • Give the students a large diagram the electromagnetic spectrum. Starter of the electromagnetic spectrum to • What the term „frequency‟ Rainbow – Get the students to list the colours of the spectrum in order. Then ask annotate over the next few lessons. means in relation to a wave. them to explain how they can split white light into these colours. (5–10 minutes) They can add uses and dangers to it • That all electromagnetic as they go. What’s a wave? – Give the students a set of cards with wave properties and non-wave properties. Can they waves travel at the same • Provide templates to help the separate them into two piles? Make sure you include one with „needs a material to travel along‟. (5 minutes) speed in a vacuum. students perform the calculations. Calculating speed – Can the students remember how to calculate the speed of something? Ask them to • How to calculate the • Gifted and talented write down the equation and answer a couple of simple speed questions. (10 minutes) wavelength of an Electromagnetic waves in other electromagnetic wave. media Main The students have been told that • Throughout these next few topics it will be useful to have a large diagram of the electromagnetic electromagnetic waves all travel at spectrum on the wall so that you can refer to it regularly. the same speed in a vacuum, but is • The students will have studied the electromagnetic spectrum at Key Stage 3, but many will be unfamiliar this true of other media? They can with the word „electromagnetic‟. find out about how the speed • It is important to get across the idea that the electromagnetic waves travel best through empty space: a depends on the wavelength and how vacuum. When doing this, they all travel at the same speed (which is the maximum speed at which anything this leads to dispersion in prisms can travel). and lenses. • Also emphasise that the spectrum is continuous: there are ranges of each of the regions. This idea can be • Learning styles shown by discussing the range of different wavelengths of red pointing out that there is not just one „red‟. Visual: Drawing wave models. • When discussing wave diagrams see „Practical support‟. Intrapersonal: Understanding the • You may wish to demonstrate some of the devices that use regions of the electromagnetic spectrum. nature of electromagnetic radiation. While doing this, point out that most of them are producing or detecting energy that we cannot see. • Homework. The students can • The main difficulty in the calculations will be the rather difficult numbers that electromagnetic waves reinforce their understanding of the present. You may find that some calculators cannot cope with them. Standard eight digit calculators cannot wave equation by trying some display 300 000 000; you may have to deal with velocities measured in kilometres per second instead. further calculations. • The students will have to take great care when performing the calculations and may find them easier if they „cancel the zeros‟ in some of them, so that they end up with simple calculations like 3/9. Risk assessment. • With students that are more mathematically able, you may wish to use numbers in standard form, e.g. 3.0 x 108 m/s. None Pupil development Pupils produce a poster detailing the uses, dangers, properties and sources of a fraction of the EM spectrum. This can be mounted on a roll of papers showing the wavelength of light changing. Research can be done from textbooks or from leaflets available on request. Plenaries Quick calculations – Show the students the wavelength of a few electromagnetic waves and ask them to quickly work out the wave speed and write it on their mini-whiteboard. (5–10 minutes) More uses – Ask the students to describe one extra use for each of the regions of the electromagnetic spectrum. (10 minutes) RMIVUXG? – The students may know an acronym to give the order of the visible light spectrum (ROYGBIV). Can they think up a method of remembering the regions of the electromagnetic spectrum? (5–10 minutes) e.g. Remember My Instructions Visible Under X-ray Glasses Learning Outcomes Practical support Most students should be able to: Drawing and labelling waves • State the parts of the electromagnetic spectrum in order of wavelength. Wavelength is a reasonably simple concept, but many mistakes are made drawing • Give definitions of the words frequency and wavelength. and labelling waves in examinations. Point out that the wavelength can also be • Describe the properties that all electromagnetic waves have in common. measured from trough to trough, or in fact any point in a wave to the next point that • Use the wave speed equation to calculate wave speed. is doing exactly the same thing. Watch out for students who draw the wavelength incorrectly; this is usually from the point where the waves crosses zero displacement Some students should also be able to: to the next zero, i.e. half a wavelength. A similar problem arises when labelling the • Rearrange and use the wave speed equation. amplitude on wave diagrams. This must be from the peak to the zero displacement position, i.e. half of the „height‟ of the wave not the full „height‟ as many students Additional Links: draw. http://www.brainpop.com/science/energy/electromagneticspectrum/ Equipment Pens and sugar paper Chalk (to draw wave) Electromagnetic spectrum books / leaflets AQA GCSE Science: P1b 5.2 Gamma rays and X-rays: reach the parts that other wavelengths cannot reach. AQA Specification Link • Different wavelengths of electromagnetic radiation have different effects on living cells. Some radiations . . . . may cause cancerous changes and some may kill cells. • The uses and hazards associated with the use of each type of radiation in the electromagnetic spectrum. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of electromagnetic radiation • to evaluate methods to reduce exposure to different types of electromagnetic radiation. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Special needs. Present each • X-rays are used to produce Lesson structure student with a photocopy of an X- images of fractured bones. Starter ray photograph so that they can • Gamma rays are used to X-ray vision – A certain alien superhero has the ability to see through objects by label the areas where the X-rays sterilise objects and to treat firing X-rays from his eyes. Ask the students to explain why this would not work pass through or are absorbed. cancer by radiotherapy. • Learning styles • Both X-rays and gamma and might not be too healthy for the people he is looking through. (5 minutes) Kinaesthetic: Manipulating and rays can damage cells or Definitions – Show the students the key words for this spread, „absorb, reflect, emit‟, and ask them to write examining X-ray images. cause cancer by ionisation down their own definitions. (5–10 minutes) Visual: Observing X-rays. processes. What’s up Doc.? – Show the students a range of X-ray photographs and ask them to describe the problems Auditory: Explaining how X-rays they see. If you don‟t have originals, then you can find some obvious ones on the Internet. (5–10 minutes) are produced. Interpersonal: Discussing injuries. Main • ICT link-up. If you have no other • Start by discussing X-rays. The images are negative; the areas on the film image that are black have source of X-rays, then the Internet been exposed to X-rays while the white areas haven’t. This shows that the X-rays have penetrated the is a great source. To make them soft tissues but have been absorbed by bones. An Animation is available on the GCSE Science CD to more realistic you could photocopy help explain this. the images onto transparencies. • This can lead to a discussion of why X-rays are harmful; the energy is absorbed in the body and Search on an image search engine damages cells, particularly cells in bones. for phrases like „X-ray jaw‟ and „X- • You can also discuss the reason X-rays are absorbed by bone; it contains materials that are more dense, ray chest‟ to find particular injuries. particularly calcium. You could also find the analyses of • This absorption by metals can be explained by using X-rays of fillings where the metal absorbs virtually all the images so you know what is of the X-rays. X-rays of plates and screws in legs always fascinate. wrong. • The difference between X-rays and gamma rays is basically how they are produced. X-rays are produced • Science @ work. The cobalt-60 when high speed electrons are stopped by dense metals; the kinetic energy is converted into the X-rays. source used in these machines is Gamma rays are produced by changes in the nuclei of atoms, these nuclear processes will be described in the very active. One such machine next chapter. accidentally ended up being • When talking about the safety precautions, you might like to ask the students what a dentist or doctor does recycled in Mexico without the when taking an X-ray. source being removed first. The • You may have a film badge to show the students, or you could mock one up from some plastic and resulting steel was sent around the aluminium. These badges offer no protection but they can be used to spot damage after the event. world and only discovered when used in construction in the Los Pupil Development Alamos research centre in New Give out X-ray images on acetates and have pupils write a brief description of what each one shows. Why Mexico, where it set off the do bones show up but skin and muscles don‟t? What is it that bones have in that cause the difference. What radiation alarms. At least one other materials show up vividly? person has died from exposure to Gamma Rays are sometimes used to inspect building safety. How do you think they are used? the resulting radiation, possibly several more. Plenaries X-ray safety – Ask the students to draw illustrations showing how dentists or Risk Assessment. doctors reduce exposure to X-rays or gamma rays. (5–10 minutes) Radiation danger – Give the students the hazard symbol for ionising radiation and explain what it is None supposed to represent. The students should add a list of safety precautions to the symbol; perhaps as icons below it. (5–10 minutes) The unknown – X-rays got their name because „x‟ represents the unknown. Can the students think up a better name for them now that they understand their properties? (5 minutes) Learning Outcomes Practical support Most students should be able to: X-rays • Describe how X-rays pass through some materials but not others and this can be used to see the It may be possible to acquire an X-ray cassette from a local hospital or even internal structure of some objects. dentist. They may also be able to provide help with obtaining X-ray images • List some of the uses of gamma rays. which are much better to handle than copies on paper. There may be • Describe the effects of gamma rays and X-rays on living cells. confidentiality issues to deal with, but it is worth asking. Some students should also be able to: Equipment • Explain, in detail, how gamma rays and X-rays damage cells. X ray acetates Additional Links: OHP http://www.brainpop.com/science/energy/electromagneticspectrum/ AQA GCSE Science: P1b 5.3 What does a bee see? AQA Specification Link • Different wavelengths of electromagnetic radiation are reflected, absorbed or transmitted differently by different substances and types of surface. • When radiation is absorbed, the energy it carries makes the substance which absorbs it hotter and may create an alternating current with the same frequency as the radiation itself. • Different wavelengths of electromagnetic radiation have different effects on living cells. Some radiations mostly pass through soft tissue without being absorbed, some produce heat, some may cause cancerous changes and some may kill cells. These effects depend on the type of radiation and the size of the dose. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of electromagnetic radiation • to evaluate methods to reduce exposure to different types of electromagnetic radiation. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: Lesson structure • Gifted and talented. Why does the • Ultraviolet radiation has a higher Starter skin become tanned when exposed to frequency than visible light. Tanning – Ask the students to describe how to get a suntan or how to avoid sunlight? The students could find out • UV light can be used to cause skin getting one. (10 minutes) what is happening to the skin and tanning and causes fluorescence. how changing colour helps protect the Filters – Shine a bright white light through a series of filters and ask the students to explain what • EM waves may be absorbed, skin from further damage. They is happening with a diagram. Use some combinations of filters. (5–10 minutes) reflected or transmitted by different should make a brief report on the Fairground attractions – Can the students come up with explanations why some media. effects. clothes glow on fairground rides and discos; ask then to explain where they think the energy comes • Learning styles from for this to happen. (5 minutes) Kinaesthetic: Carrying out suncream experiments. Main Visual: Observing UV effects. • Show pupils the Ultraviolet powerpoint (see link below) to show that other Auditory: Explaining fluorescence. animals such as insects, rats and bird can see colours that we cannot. Interpersonal: Debating the • It is useful to demonstrate how ultraviolet can be used here, but great care healthiness of a tan. must be taken with ultraviolet lamps and demonstrating fluorescence; see Intrapersonal: Evaluating the ‘Practical support’. Many students will have seen the fluorescent effect at effectiveness of suncream. fairgrounds or discos. • ICT link-up. Using a UV detector, you could monitor the UV levels • Check that the students understand that the ultraviolet light is being absorbed and the energy is throughout the day and the students then being reemitted as visible light; some think that the ink is giving out ultraviolet light. could explore the results and discuss • If you have a pair of sunbed „goggles‟ and a ultraviolet photodiode or ultraviolet sensor, you may what times it is safer to go out in. like to test them to demonstrate the importance of wearing them. How much longer could you stay out • During the discussion about the interaction of electromagnetic waves and materials, check in the morning compared to mid-day, understanding of the key words, especially „transmitted‟. Use the simple idea that glass transmits and still get the same dose of UV? visible light. You might want to use an X-ray and link back to that. • Try to get across the idea that the waves can carry a signal that can be picked up by a material when energy is absorbed by it. Pupils development Darken the room and let the lamp warm up for a few seconds before use. Shine it onto the washed cotton and it should glow noticeably (some washing powders seem to work better than others). Write on an object with the security markers and use the light to reveal the writing. During the demonstration some students will say that they can see the UV light; make sure you point out that this is merely violet light that is also produced by the bulb. Pupils could also investigate the absorbance of UV light by different factors of sun cream. Debate why it is important to use sun cream. What might someone with sun cream on look like to a bee!? How does sun cream work? Fluorescing materials emit more visible lights than they absorb. What do you think is going on?? We also have a recent addition of beads that are white in plain light but fluoress different colours on exposure to UV light. Possible experiment with sun cream factors. Plenaries UV summary – The students produce a small table summarising the dangers and uses of UV light. (5–10 minutes) UV and glass – A glass block absorbs UV light, but transmits visible light. The students must draw a diagram explaining this without any words. (5–10 minutes) Cancer cover up – Students design a poster to warn about the dangers of UV radiation causing skin cancer. (15–20 minutes) Learning Outcomes Practical support Most students should be able to: Demonstrating fluorescence with UV light • Describe the uses and dangers associated with UV Equipment radiation. NB: These use of UV equipment is best in a blacked out lab. • Draw diagrams illustrating the concepts of reflection, UV lamp – excellent for looking at £10/£20 notes and your drivers licence! transmission and absorption. UV security marker Fluoresent materials (Fluorite, highlighters, Cash notes, stamps ect) Some students should also be able to: White cotton recently washed in biological washing powder (or use pupils clothes) • Explain what happens in reflection, transmission and Different factors of suncream. absorption in terms of energy. Energy beads, in Petri dishes with sunscreen over in the big UV light thingy from technology Additions Risk assessment. UV lights can damage eyes when directly exposed. You must be cautious with the UV lamp in this demonstration. UV Ultraviolet.ppt will damage the retina; the lamp must be used so that the students, and yourself, can never look into the bulb. This is especially important in a darkened room. AQA GCSE Science: P1b 5.4 Remote controls, microwaves and radios. / Transferring Information AQA Specification Link • The uses and the hazards associated with the use of each type of radiation in the electromagnetic spectrum. • When radiation is absorbed, the energy it carries makes the substance which absorbs it hotter and may create an alternating current with the same frequency as the radiation itself. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of electromagnetic radiation • to evaluate methods to reduce exposure to different types of electromagnetic radiation. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Gifted and talented. If you carry • How microwaves heat Lesson structure out the microwave experiment (and material when they are Starter the transmitter is a polarised one; it absorbed by water molecules. Infra-red recap – The students should produce a quick recap of what they know usually is) you may like to • The ways in which infra-red, about IR already. A spider diagram would be ideal. (10 minutes) challenge the students to find an microwaves and radio waves explanation for polarisation. Point are used in communication the transmitter and receiver directly Main systems. at each other and switch on to show • The first part of the lesson is basically a recap on the properties of infra-red radiation. the maximum signal. Position a • The students should already be familiar with the heating effect of IR from a previous topic, but it is worth metal diffraction grille (a set of showing an IR heater again as reinforcement. vertical wires) between the • Demonstrating an infra-red remote control should be fairly simple but the students may not be transmitter and receiver and rotate aware that the IR can be reflected, so try turning some equipment on by reflecting the signal off the it. The signal should vary from whiteboard. maximum to zero just by rotating • Students may also be aware of IR transmitters on their mobile phones that can be used to transmit the plate. information short distances. You may like to investigate the maximum distance a message can be sent • Learning styles from. Discuss why! Kinaesthetic: Investigating IR Work through Pages 288/289 of book and answer summery questions in book or use summery communications in the practical questions from P1b 5.4 (can be given as H/W) activity. • You might be able to block a radio signal by placing an earthed aluminium foil shield around it so that you Visual: Observing the transmission can explain that radio waves may be absorbed. and blocking of signals. • More modern mobile phones are equipped with Bluetooth technology. You can discuss this as superior Auditory: Discussing development communication systems to the IR mentioned above. of phone communications. Interpersonal: Making deductions Plenaries about what is happening to Wave disasters – How can each type of electromagnetic wave be used to send an emergency or warning electromagnetic waves. signal? Can the students think up ideas for all of them (e.g. visible light and lighthouse)? (5–10 minutes) Intrapersonal: Debating harm What’s the frequency? – Give the students the frequency of some local radio caused by microwave radiation. stations and ask them to work out the wavelengths (and vice versa). (10–15 minutes) Learning Outcomes Pupil Development Most students should be able to: • List the ways in which infra-red waves, microwaves and radio waves are Testing infra-red signals used. Infra-red signals are able to pass through several paper sheets as long at the batteries on the remote are • Describe the relationship between the wavelength and frequency of these in good order. waves. Simply place layers of paper over the transmitter one at a time to find out how many layers are needed to block the signal. You should find that larger transmitters, such as those for TVs, can send a signal Some students should also be able to: through at least three sheets. Low-power transmitters, such as those operated by a button cell, struggle • Describe how alternating currents can be used to produce radio waves. to get a signal through two sheets. • Describe how radio waves induce alternating currents in aerials. Test the distance of transmitting information through mobile phones. Which works better, infra red or Bluetooth? Why do you think this is? Equipment. Pupils can use their mobile phones in this lesson. Alternatively a Television and remote control can be used. Meter rules Paper IR theremometer IR heater W/Sheet P1b 5.4 Risk assessment. None AQA GCSE Science: P1b 5.5 Radios, Mobile phones, satellites and televisions AQA Specification Link • Radio waves, microwaves, infra-red and visible light can be used for communication. • Microwaves can pass through the Earth‟s atmosphere and are used to send information to and from satellites and within mobile phone networks. • Infra-red and visible light can be used to send signals along optical fibres and so travel in curved paths. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Gifted and talented. The students • That microwaves and radio Lesson structure could investigate the relationship waves are used in mobile Starter between wavelength, the size of phone networks. Get the message across – The students must think up as many ways as possible to gaps and the amount of diffraction • How the atmosphere, communicate information. List as a mind map on the board and discuss how the that takes place. including the ionosphere, • Learning styles affects the range that different information travels. (10 minutes) Kinaesthetic: Investigating total waves can travel. Mix up in communications – Give the students a set of cards with communications technologies and internal reflection. • How optical fibres can be electromagnetic waves and media that carry them and ask them to sort them out. (e.g. TV, radio waves, air). Visual: Observing optical fibres. used to carry waves allowing (10 minutes) Auditory: Listening to a discussion them to be contained and Reflection – Can the students make a device to see around corners and explain how it works? They could of IT communications systems. travel around bends due to just design it or perhaps even make it. (10–15 minutes) Interpersonal: Collaborating in total internal reflection. practical activity. Main Intrapersonal: Considering • The advantages of using higher frequency waves for communication are important. evidence from the practical activity. • The concept of diffraction may not be well understood; it is typically shown by discussing waves passing • ICT link-up and spreading out over hills. • One of your network technicians, • You can show the diffraction effect of waves with a ripple tank. or IT teachers, could present a brief • Many students will not be aware that the atmosphere has many layers; you may wish to take a bit of time talk about the schools wireless and show them a diagram of its structure from the Earth‟s surface to space. network. • Using a globe to explain how the waves can reach places below the horizon is very helpful. You may find students‟ geography knowledge is weak when you are discussing communications over long distances, so it is good to show them the places you are talking about. • If you are talking about satellite TV, you may wish to briefly mention the geostationary position of the satellites and the distances involved. With a typical globe (diameter 30cm) the satellite would be nearly 1m above the surface. This is part of the reason that satellite transmissions for communications show a „time lag‟. • Demonstrate or allow the students to discover total internal reflection. See „Practical support‟. • Demonstrate the optical fibre, see „Practical support‟. • If you have a model optical fibre, a large curvy block designed to show multiple total internal reflections, you can show how the ray is contained within the glass; no energy leaves the glass. • Optical fibres are used in endoscopes in medicine and also by spies and the military for seeing through walls or around corners. You may be able to find video clips of their use. Plenaries Round the bend – Give the students a diagram of an optical fibre in a reasonably contorted path and ask them to draw the path of a ray that is shown entering the fibre. (5 minutes) Sorry for the inconvenience – The students should design a leaflet from a TV or satellite TV company explaining why the television signal has been poor recently. (15–20 minutes) Abbreviation dictionary – The students have encountered a lot of abbreviations over the past few lessons; they should make a list of these and their meanings. (10 minutes) Learning Outcomes Practical support Most students should be able to: Optical fibres are easy to demonstrate in a lab even in fairly bright conditions. • Draw a simple diagram of the ways radio waves travel in the atmosphere. Bend the fibre around several objects (perhaps the whole room). Don‟t bend it too much • State that satellite TV signals are carried by microwaves. though, or the glass may crack; anything smaller than a 10 cm radius is dodgy. Allow • Draw a diagram explaining how light or infra-red waves travel along an optical fibre. one student to observe the distant end while you flash a torch into the near end. Even with the thinnest of fibres, the transmitted light should be obvious. The students can pass Some students should also be able to: the fibre end along while the light is flashing. • Explain why microwaves can be used for satellite communications. Equipment and materials required Additions Fibre optics kit Ripple tank http://laser.narr.as/laser.swf - a great game where a laser beam can be reflected, refracted Globe and split! Diffraction.ppt – Powerpoint showing the principles of diffraction and fibre optics AQA GCSE Science: P1b 5.6 Analogue and digital radio, why make the switch? AQA Specification Link • Communication signals may be analogue (continuously varying) or digital (only on and off). Digital signals are less prone to interference than analogue and can be processed by computers. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Special needs. Provide the • The differences between Lesson structure students with an analogue signal analogue (continually Starter graph already drawn and a table to varying) and digital (binary) Sound quality – Play the students a sound sample from a scratched record (or a real fill in. They encode the graph and information. scratched record), ask them to explain what has happened to the sound to reduce the then try to redraw it from the • That digital signals are less quality. You can also try this with a poor quality video cassette. (10 minutes) numbers on another pre-prepared prone to interference and Digital storage – How much information can various digital devices store? The students set of axes. noise effects and are simpler may be aware that a personal music player can hold 5 megabytes, but what does this • Gifted and talented. Digital for computer systems to mean in terms of songs and in terms of bits? (10 minutes) messages can become corrupted and handle. Information overload – The students are given a set of cards with devices on them, distorted in a number of ways. The and have to sort them into order by the amount of information (or music) one can signal may spread as it passes along long fibres, or the noise level may hold. Examples include a LP record, tape, CD, DVD, hard disk, digital video be so high that bits are corrupted. cassette and human brain. (5 minutes) Computer systems are designed to be able to correct for these errors Main automatically. The students can find • The difference between analogue information and digital information can be shown out the basics of these problems and by showing a CD and a vinyl record. The CD contains a series of very small pits, how they are detected and representing a set of 0s and 1s, while the record has a groove that varies continually corrected. from side to side. • Learning styles • You may be able to see this groove with a microscope (or better still a video Kinaesthetic: Modelling analogue microscope) but you may have to break the record. and digital graphs. • It is important to show some optical fibres to show that visible light can be transmitted Visual: Drawing and observing along it. If you didn‟t do this on the last spread, then use the opportunity here. analogue and digital information. • You should point out how thin the actual fibres are; most of the cable is actually Auditory: Listening to differences protective wrapping to make it easier to handle. in signal quality. • Try the analogue to digital conversion activity (see „Practical support‟) to give an idea of how this conversion can be done. If time is short, you could provide the data to plot and the students can compare their results with your original. • You might want to show how a letter can be encoded into binary bits in a byte. For example in ASCII, see „ICT link-up‟. • It is simple to show the idea of a carrier wave to transmit a digital signal; just turn a torch on and off. The signal is the pattern of on and off, while the carrier is the electromagnetic wave. • ICT link-up. In ICT, characters are encoded into sequences of • Modulation is a much more difficult concept to get across, especially frequency binary numbers. A simple system is modulation. With visible light, amplitude modulation would result in changes of the called ASCII (American Standard brightness of the light, while frequency modulation would result in slight changes of Code for Information Interchange), colour. Try to discuss these ideas, but don‟t be too worried if there are difficulties. where each character is represented • To show how easy it is to recognise a digital signal, show a diagram of a fairly badly by a pattern of seven bits plus an corrupted one with noise spikes, and see if the students can translate it back into 0s error check bit making a total of and 1s. eight bits or a „byte‟. This allows for 128 possible characters, Plenaries including the alphabet, numbers and Analogue or digital – Give the students a set of cards and ask them if the information or punctuation symbols. For example communication method is analogue or digital. Include things like TV signals, MP3 „a‟ is represented by the sequence players, tape recorders, phone signals, voices, etc. (5 minutes) 01100001 and „b‟ by 01100010. Communication crossword – The students should complete a crossword based on the More modern encoding systems are electromagnetic spectrum and communications. (15 minutes) more complex allowing millions of Decoding – Give the students a binary code and a key to decode it, and see who characters. can find the exit code first. (5 minutes) Learning Outcomes Pupils Development Activities and extensions Most students should be able to: Ask the students to draw a set of axes on the graph with 0–7 on the y- Sending a message through a • Describe the differences between an analogue and digital signal. axis representing signal strength, and 0–15 on the x-axis representing fibre • List the advantages that digital signal transmission has over time. They should then draw a random wave along the graph moving Can the students send a message analogue. from left to right. Next they need to digitise this analogue wave. They through an optical fibre? You can should convert it into a table of numbers, but only integer numbers are set them this challenge for Some students should also be able to: allowed; so for every value of x they must write down the nearest homework, or as a simple task • Describe how an analogue signal can be converted to a digital one whole number on the y-axis. Next they pass this table of data to another during the lesson. For homework, and vice-versa. student, and ask them to plot a graph of the data and connect the points they would have to come up with an with a wave without seeing the original. After finishing, they can encoding system of their own. Additions compare the two. Discuss how the copy can be made more accurate Don‟t tell them what the message is Diffraction.ppt – The end of this Powerpoint contains a section on (greater resolution: 0–15 on the y-axis; faster sampling: 0–30 on the x- going to be in advance. analogue and digital signals. axis) and what advantages and problems this would have. This method leaves out the time consuming conversion to binary and back. Equipment Graph paper Rulers Risk assessment None AQA GCSE Science: P1b 5.7 Can mobile phones cook your brain!? Or if Brainiac clip is available “How many mobile phones to boil an egg” AQA Specification Link Substantive content that can be revisited in this spread: • The electromagnetic spectrum is continuous but the wavelengths within it can be grouped into types of increasing wavelength and decreasing frequency: gamma rays, X-rays, ultraviolet rays, visible light, infra-red rays, microwaves and radio waves. • The uses and the hazards associated with the use of each type of radiation in the electromagnetic spectrum. • When radiation is absorbed, the energy it carries makes the substance which absorbs it hotter and may create an alternating current with the same frequency as the radiation itself. • Different wavelengths of electromagnetic radiation have different effects on living cells. Some radiations mostly pass through soft tissue without being absorbed, some produce heat, some may cause cancerous changes and some may kill cells. These effects depend on the type of radiation and the size of the dose. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of electromagnetic radiation • to evaluate methods to reduce exposure to different types of electromagnetic radiation. Teaching suggestions Activities As mentioned in title, Brainiac has a good clip where 100 mobile phones are piled over an egg and then called to see if the combined heat would cook the egg. Natch it doesn’t! Selling the radio spectrum – Mobile phone companies actually paid over £22 billion for their 3G UK licences, nearly making some of them bankrupt. The government used some of this to pay off debts from World War Two! Another large amount will be raised when the analogue TV bands are sold off. What do the students think should be done with this money? The allocation of the spectrum is now controlled by Ofcom and their web site contains a complete breakdown of the uses of the radio spectrum. Search their site for the „frequency allocation table‟; it is a bit technical in parts, but it‟s interesting to see the varied uses of the frequencies. A key scientific invention – By late in the war, radar had developed so much that a submarine could be detected at a range of several kilometres, even if it just popped up to replenish oxygen supplies or receive radio orders. The survival rates of U-boat crew were very low in the last couple of years of the war. The Germans tried to develop a U-boat that could stay under water for much longer, but the project was too late and the battle had already been lost. Once the convoy routes were secure, the build up to D-Day could begin. You may like to look into „stealth‟ technology developed to reduce the radar signature of planes and some ships. If you are discussing these ideas, then make sure that the students do not confuse radar with sonar. The big switchover – Some areas of the UK have already switched entirely to digital transmissions, such as Llanstephan in Wales, as an experiment to see if it works well enough. There are still problems with digital television; not all of the country is covered by the signal, and reception is poor in a number of hilly areas. Should these people be provided with free satellite dishes? Should everybody else be given free „digiboxes‟ when the switchover comes? This could cost hundreds of millions of pounds. The students can find a map of areas covered online or search by postcode; search for „freeview coverage‟. Mobile phone hazards – You may have had a discussion about mobile phone hazards at the beginning of the chapter. If you have, you can briefly revisit the idea and see if any of the students have changed any of their opinions in light of their new knowledge. The debate here could be more focused on the social aspects of mobile phone use: where should they and where shouldn‟t they be allowed and the accidents that can happen when using them. There are many campaign sites available on the Internet, some with detailed information and others with vague assertions. This evidence must be evaluated before being used in any debate. Extension or homework The poster activities can be carried out at home, as can the research for the phone debate. http://imagers.gsfc.nasa.gov/teachersite/wavstown.pdf ICT link-up/activity Information required for the debate on mobile phones and their masts is available on the Internet from a variety of sources. The students will need to evaluate the reliability of this information based on the agendas of those producing the sites; from phone companies, the government and campaign groups. This is useful for teaching about societal influences, required in the „How Science Works‟ section of the specification. Learning styles Kinaesthetic: Role-play of mobile phone debate. Visual: Obtaining information on phone maps. Auditory: Discussing a range of issues. Interpersonal: Discussing and debating. Intrapersonal: Evaluating evidence from Internet research. Gifted and talented How does radar work? The students can make a booklet or presentation explaining how radio waves can be used to detect objects. They can even look into ways of avoiding being detected by radar, such as the common film tactic of „flying in below the radar‟. AQA GCSE Science: P1b 6.1 Observing nuclear radiation AQA Specification Link • The basic structure of an atom is a small central nucleus composed of protons and neutrons surrounded by electrons. • Some substances give out radiation from the nuclei of their atoms all the time, whatever is done to them. These substances are said to be radioactive. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Learning styles • The basic structure of an Lesson structure Kinaesthetic: Modelling the atom. Starter structure of an atom. • That unstable nuclei decay Seeing the invisible – How can we detect things that we cannot see? Ask students to come up with a list of Visual: Observing demonstrations/ and emit invisible radiation things that we cannot see and how we can detect their presence, e.g. air, infra-red radiation. (5–10 minutes) computer animations and when the structure of the Atom – What does an atom look like? Ask the students to draw and label one before showing them our simulations. nucleus changes to become current (nuclear) model. Does an atom really look like this? (5–10 minutes) Auditory: Listening to descriptions more stable. Atom models – Give the students a set of cut-out protons, neutrons and electrons of nuclear processes. • That this radiation can be and ask them to make a model atom. (10 minutes) Interpersonal: Discussing the detected in a number of ways dangers of scientific research. including by a GM tube. Intrapersonal: Evaluating safety Main precautions. • Before carrying out any demonstrations involving radioactive material, make certain that you are familiar • ICT link-up with local handling rules. (See „Practical notes‟.) • The students cannot handle • Start by checking knowledge of atomic structure, protons, neutrons and electrons, as this is essential in radioactive material, but the discussing isotopes later. simulations on the GCSE Science • You can then discuss the history of the discovery of radioactivity. You should point out that although the CD allow them to explore ideas initial discovery was accidental, the investigation into the cause was a thorough scientific one. safely. These are an excellent way • Marie Curie died aged 67 partly because of her work. Similar things happened with early researchers into to visualise the behaviour of the X-rays. This shows that even scientists under-estimate the hazards of their research. particles and waves and to study • Show the presence of radiation due to the sources by using a GM tube or spark detector. (See „Practical absorption. They can also support‟.) demonstrate the half-life of • Use the Interactive Simulation P1b 6.2 „Alpha, beta and gamma radiation‟ to show the different types of materials, a process that is too radiation coming from the nucleus. difficult to show with real • Emphasise that nuclear radiation is caused by changes in the nucleus. You could link back to the difference substances in class. However, it is between X-rays (caused by electrons) and gamma rays (caused by the nucleus). best to use these simulations • You might ask the students to draw the nucleus of a couple of isotopes to check that they understand the alongside real apparatus if possible, term. If you do this, it is worth reminding them that the nucleus is really spherical; not just a disc. Show a to show that the models are linked model made of marbles stuck together; if one falls off, then attribute it to nuclear decay. to physical reality. • If you do not • Some students may like to know why the nucleus decays. The reason for the nucleus changing is linked to want the student to get too close to energy. The nucleus changes so that it has less energy; the parts that make it up have become more tightly the sources, then you could connect bound; this is yet another example of energy spreading out. a small video camera to a data projector to show the Plenaries demonstrations more clearly. Isotope analysis – The students are given a list of isotopes to draw the structure of, or diagrams of nuclei for them to describe. They could use a periodic table to help identify the element. (10 minutes) Murder mystery – The body of a press photographer has been found in a sealed room, all of the film in her camera has gone black even though it hasn‟t been used. Write a letter to the police explaining what you think happened and how you know. (5–10 minutes) It’s elementary – Give the students a list of recently discovered elements and see if they can figure out what they are named after (Californium, Curium, Nobelium, etc). What would the students call an element that they discovered? What symbol would it have? (5 minutes) Learning Outcomes Practical support Most students should be able to: Demonstrating radioactive sources safely • Draw a diagram illustrating the structure Radioactive sources can be used to demonstrate important aspects of this chapter, but there are important safety considerations to take of an atom (nuclear model) into account. Your school should have a set of local rules that apply to the storage and handling of radioactive sources, and these should • State what we mean by a „radioactive‟ inform you as to the ways to handle practical activities. You should make the students fully aware of the dangers associated with the substance. sources, but also emphasise that you will be handling them with great care and they are in no danger as long as they too follow sensible • Describe ways in which radioactivity procedures. You should discuss the reasons for the safety points below with the students: can be detected. • Do not handle radioactive sources until you have had a training session from the school Radiation Protection Supervisor. • Under no circumstances allow the students to handle the sources. Some students should also be able to: • Always minimise exposure; keep the sources in the storage container whenever they are not being used and only demonstrate with the • Explain why some substances are sources for the minimum time possible to get the concept across. radioactive. • Always handle the sources with tongs away from the trunk of your body to minimise exposure. • Perform experiments in a large tray, so that if sources are dropped they do not roll and fall to the floor. • Check all sources are returned to the storage container and storage facility before the end of the lesson. Using a GM tube and ratemeter The usual way of showing the presence of ionising radiation is by using a Geiger Müller tube and ratemeter. This has the advantage that the count rate is proportional to the activity, and some of the students will be familiar with the device from films and television. Equipment and materials required Details The operating voltage of the GM tube is usually 400V and this is usually provided by the ratemeter, but you may need an external supply for tubes that connect to computers. Check with the manual if you still have it. Position the detector in the tray and switch it on. Bring the sources close to the tube window and the ratemeter should count. If you can find a ratemeter that clicks, the demonstration is a lot more fun. Equipment Geiger Müller tube ratemeter (and possibly high voltage power supply) large plastic tray tongs radioactive sources lab coat Lead shielding Meter rule Risk assessment Make sure you speak with technicians for a full risk assessment when using radioactive samples. AQA GCSE Science: P1b 6.2 Aplpha, beta and gamma radiation AQA Specification Link • The characteristics and properties of the three main types of nuclear radiation emitted by radioactive sources: alpha particles, beta particles and gamma rays. • The uses of, and the dangers associated with, each type of nuclear radiation. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of nuclear radiation • to evaluate measures that can be taken to reduce exposure to nuclear radiations. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Gifted and talented. Where do • The different radiations Lesson structure the beta particles come from? The have different penetrating Starter beta particles are high-energy powers because they are Magnetism – The students should be familiar with magnetic fields. Ask them to show their knowledge in a electrons that come from the absorbed by materials as they diagram/mind map/spider diagram. (10 minutes) nucleus, but there are no electrons pass through. It’s all Greek to me – Scientists use a lot of symbols in their work. Discuss the reasons that scientists use in the nucleus! The students need to • The range in air is different symbols for elements, equations, the names of things, etc. You might ask the students to list all of the find an explanation of what is for each type of radiation and symbols that they know the meaning of; they know more than they think. (5–10 minutes) happening in the nucleus that is that they are affected This isn’t a Biology lesson! – Ask the students to draw and label the important parts of an animal cell. They producing these electrons. differently by electric and should explain where the genetic information is stored. (5–10 minutes) • Learning styles magnetic fields. Kinaesthetic: Modelling with • Nuclear radiation is ionising Main simulations. and this damages living cells • The Interactive Simulation P1b 6.2 „Alpha, beta and gamma radiation‟ show the different types of radiation Visual: Observing demonstrations. causing cancer or cell death. coming from the nucleus. A simulated experiment allows students to test what different types of radiation Auditory: Explaining effects of can penetrate. radiation. • You may demonstrate the penetrating powers of radiations with the method set out in „Practical support‟. Interpersonal: Discussion of • The difference between alpha and beta particles and the electromagnetic wave nature of gamma should be radiation. emphasised. Intrapersonal: Interpreting evidence • Gamma radiation causes no change in the structure of the nucleus; it is really the nucleus dumping some from demonstrations. excess energy it didn‟t lose in a previous decay. • The lack of charge on the gamma rays accounts for their higher penetrating power; they interact with matter a lot less than alpha or beta. • Depending on the structure of your course, the students will probably not have encountered the idea of ionisation before. It is important that they grasp the concept of the radioactive particle stripping away electrons from atoms and causing unwanted chemical reaction in cells. • The main danger is that the cell will be damaged and reproduce out of control. Explain that this becomes more likely the larger the dose of radiation, but that it is possible for a single damaged cell to cause cancer so there is no minimum safe limit to radiation. We should therefore try to limit our exposure by keeping sources safely away from our bodies. • The students will look at the natural background radiation later, but some may have noticed the Geiger counter clicking away even when there are no sources in the room. Plenaries Local rules – The students should make a poster or booklet explaining how your radioactive sources should be stored and handled. (15–20 minutes) Summary diagram – Can the students draw a single diagram that will summarise all of the information from today? (10 minutes) Protect and survive – What if one of the radioactive sources was dropped and lost? How would it be found and what precautions would need to be taken during the search? (10 minutes) Learning Outcomes Practical support Activities and extensions Most students should be able to: Penetrating power More detectors – There are other • Describe the penetrating powers of the three radiations. The techniques used on the previous spread ways of detecting and analysing • Describe the range in air of each type of radiation, their relative ionising power and how can be expanded to show the penetrating ionising radiation, including cloud they are affected in a magnetic field. power of the three radiations. (Teacher and bubble chambers and • Evaluate which radiation is the most hazardous inside and outside of the human body. demonstration only.) photographic films. The students • Describe ways of reducing the hazards presented when handling radioactive substances. Equipment and materials required could find out about these devices Geiger Müller tube, ratemeter (and possibly and why they are used. Which of Some students should also be able to: high voltage power supply), large plastic tray, the devices reveals most about the • Explain why radiation is dangerous. tongs, radioactive sources, set of absorbers radiation and in what circumstances (paper, card, plastic, aluminium of various are they used? thicknesses and lead plates). Details Set the equipment up in the tray, as before, but add a mount to position a source in place. Between the source holder and detector position a holder to hold the absorbers. Make sure that the detector is less than 10 cm from the source holder or the alpha particles will not reach. Turn on the detector and then mount an alpha emitter in the holder and note the count rate. This function can be performed by most meters, but you may have to count for 20 seconds if not. Position a paper absorber between the source and detector and note the count rate. Test the beta source with paper, plastic and then aluminium plates. Test the gamma with aluminium and then various thicknesses of lead. AQA GCSE Science: P1b 6.3 Half-life AQA Specification Link • The half-life of a radioactive substance is defined as „the time it takes for the number of parent atoms in a sample of the substance to halve‟ or „the time it takes for the count rate from a sample of the substance to fall to half its initial level‟. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Special needs. Students should be • The activity of a radioactive Lesson structure provided with a results table with source decreases with time Starter one set of results already filled in to because the number of An exponential decay puzzle – A farmer has a warehouse with two million corn cobs in it. Every day he help explain the idea. unstable nuclei is decreasing. sells exactly half of his remaining stock. How long before he has sold every last nugget of corn? (5–10 • Learning styles • The half-life of a source is a minutes) Kinaesthetic: Practical dice activity. measure of how long it takes An exponential growth puzzle – A philosopher places a grain of rice on the first square of a chess board, Visual: Observing and presenting for the activity of a source to two on the next, four on the next and so on. How many go on the last (sixty-fourth) square? (5–10 minutes) evidence. reach half of its initial value. The big time – Give the students a set of events and time intervals, ask them to put them in order of Auditory: Explaining the evidence. duration. Examples include a second, a century, an epoch, the duration of a lesson and the time a match takes Interpersonal: Evaluating quality of to burn. (10 minutes) results. Intrapersonal: Interpreting Main evidence. • Begin by discussing the term „isotope‟. The students should be becoming familiar with the structure of the • ICT link-up atoms and should quickly grasp that the number of neutrons may vary. • The half-life of most materials • „Parent‟ and „daughter‟ are important terms also. You could show a nuclear decay equation (or a simplified available to high schools is too long one) to get these terms across. to measure in class. A simulation of • The rolling dice decay model is an enjoyable experiment, but it can take a bit of time. To improve the decay is the best way to approach average values the groups can share data and this will lead to a more precise half-life. this topic. • At the end of the experiment, make sure that the students understand that the dice represented nuclei and • Half-lives can be modelled in removing them represented decay. detail using a spreadsheet. The • They should have a reasonable understanding that the pattern is the same each time, even though we do not students could enter their results know exactly which of the dice decays each time. and plot the graph. For the more • If you feel like being a bit „all knowing‟, seal the answer in an envelope in advance and stick it to the board mathematically inclined, the in plain sight. Then „reveal‟ it at the end, which allows you to discuss the fact that we can accurately model spreadsheet can calculate a function random behaviour using mathematics. of the decay curve which should be • The experiment lends itself well to the ideas of repeating to improve reliability, but can also be used to y=y0 e-(1/6)x if results are ideal. explain that statistics work best on very large samples so the more dice the better the fit. (This relates to „Ideas of reliability of data‟ in „How Science Works‟.) • There is also opportunity to develop or assess graph plotting skills along with drawing lines of best fit. (This relates to „Presenting data‟ in „How Science Works‟.) • You can discuss what happens to the „count rate‟ after each roll. The number of dice eliminated represents this and this rate should decrease as the number of surviving dice falls. This gives the students a decent understanding of why the count rate falls as time goes on. Plenaries Careful! You can have your eye out with that! – An archaeologist claims to have found the arrow that killed King Harold in 1066. Can the students explain how a scientist would try to check this claim? (10 minutes) Coin toss – If I have 120 coins and toss them all, removing all of the heads after each toss, how many tosses until I should only have 15 left? [3 tosses.] (5 minutes) Activity and decay – Show the students a graph with three decay curves on them. Can they identify which has the longest half-life and which is the most active source? (5 minutes) Learning Outcomes Practical support Activities and extensions Most students should be able to: Radioactive dice Roll the dice – Starting with the • Define the term half-life in relation to the activity of a radioactive source. This is a simple model of the randomness of radioactive basic six-sided dice experiment, the • Determine the half-life of a source from a graph or table of data. decay and how to find the half-life. students could investigate what Equipment and materials required would happen if a different set of For each group: a set of 59 identical six-sided cubes and dice were used. Dice with 4, 8, 10, one cube of a different colour. The dice should have a dot 12 and 20 sides are available from on one face only. (You can use more or less dice gaming shops, and will produce depending on how many you have, but 60 works well.) similar exponential decay curves Details but with different half-lives. The students roll the full set of dice, and after each roll they remove the dice that landed showing a spot. They record the number of dice „surviving‟ and then roll only these dice, and so on. They continue this process of elimination for 20 rolls, or until no dice survives. During this, they should also note down when the special dice lands spot up causing it to be removed. If time permits, they repeat this process and calculate an average number of dice remaining after each roll. Plotting a graph of the number of dice remaining (y-axis) against roll number (x- axis) reveals that the dice behave like decaying atoms and a half-life can be calculated; this should be 4.16 rolls. The single dice should show that the process is random; it is impossible to predict when any individual dice will be eliminated. For some groups, it will be removed after the first roll and for others it will survive until the end. AQA GCSE Science: P1b 6.4 Radioactivity at work AQA Specification Link • The uses of, and the dangers associated with, each type of nuclear radiation. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of nuclear radiation • to evaluate measures that can be taken to reduce exposure to nuclear radiations • to evaluate the appropriateness of radioactive sources for particular uses, including as tracers, in terms of the type(s) of radiation emitted and their half-lives. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Special needs. Provide a partially • That radioactive sources Lesson structure completed flow chart for the have a number of uses Starter operation of the foil press. including thickness Radiation misconceptions – The students will have seen a range of films in which radioactive materials • Gifted and talented. Very large measurement, medical tracing have caused strange effects. Get them to list all of the things they think radioactivity can do, and then go numbers of radioactive particles are and determining the age of through them deciding if they are true or false. (5–10 minutes) produced in nuclear reactors. How materials. Just how thick? – Ask the students to measure the thickness of a sheet of paper. Can they find out if all of are these particles contained and are the sheets are the same thickness? How? (5 minutes) there any that escape into the PhotoPLUS – View and discuss the PhotoPLUS on „Radioactive issues‟, available on the GCSE Science environment? The students may CD. (10 minutes) find out about neutrons and neutrinos. Main • Learning styles • Using radioactivity to determine the thickness of a material is a fairly straightforward idea; you can link it Kinaesthetic: Researching into to the idea of light being absorbed by paper. How many sheets of white paper will stop all light passing dating techniques. through it? Visual: Observing absorption • The function of the foil press can best be shown as a flow chart with terms like: „Is too much radiation demonstration. getting through?‟→„Open up rollers a bit.‟ Auditory: Reading aloud • Demonstrate that the thicker a material is the less beta radiation passes through. This could be a quick information. demonstration as in „Practical support‟, or you could look into it in more depth. Interpersonal: Discussing uses of • When discussing radioactive tracers, you may be able to find a video clip of a tracer being used in the body radioactivity. to find a blood vessel blockage. (For example, search an image bank for „radioactive tracer‟.) Intrapersonal: Understanding • The students should be made aware that the tracer must be picked for the job based on a range of factors, radiometric dating techniques. including the type of radiation it emits (gamma) and its biochemical properties, i.e. will it build up in the • ICT link-up. A simulation of the organ we want it to? absorption of beta particles by • There are isotopes suitable for a wide range of medical studies, some of which are artificially generated in various resources is available. The nuclear reactors. students can find out for themselves • You may want to talk about tracers used to find gas leaks and monitor the path of underground rivers. how the particles are absorbed by These too are carefully chosen. different materials. • Carbon dating is only useful over a certain range of times and the materials must be organic. The limit is about 50 000 years, which is good enough for all recorded human history. • It also needs to be calibrated against objects of known ages; ancient trees are handy for this. Ask the students how we know the age of these trees. • Uranium dating is generally used to date rocks and is part of the evidence for the Earth being 4.5 billion years old. • There are some assumptions that are made with dating processes and you may wish to discuss these with the students. Do the levels of carbon-14 remain constant in the atmosphere? Is there any other way of lead being produced in rocks? Plenaries The dating game – Give the students a set of cards of historical events and a set of „radioactive activities‟ that have been measured for artefacts from these events. Ask the students to match them up. (5 minutes) The right isotope – Can the students match the isotope to the job it is used for? Give them a list of isotopes, the type of emitter they are and their half lives and see if the students can decide what they would be useful for. (10 minutes) Radioactivity’s great – Radioactivity has a fairly bad press; the students should produce a poster expounding the virtues of radioactive material. (15–20 minutes) Learning Outcomes Practical support Most students should be able to: Demonstrating absorption • Describe how a beta source can be used to measure the thickness of a material like See local rules for handling radioactive sources. It is possible to show how aluminium foil. radioactivity can be used to measure the thickness of materials. (Teacher • Describe how radioactive traces are used in medical analysis. demonstration only.) • Describe how radioactive isotopes can be used to determine the age of a rock or organic Equipment and materials required material. GM tube and rate meter, set of aluminium absorbers, beta source, tongs. Details Some students should also be able to: Mount the GM tube and absorber holder in line with the source holder. Position the • Evaluate the properties of a radioactive isotope to determine why it would make a good source carefully and record the count rate (or take a count over 30 seconds). Test the medical tracer. aluminium absorbers one at a time, noting the decreasing count rate as the thickness • Find the age of an organic sample from date presented to them. of the aluminium increases. You may wish to get the students to plot a graph of count rate against absorber thickness to determine how much aluminium is required to reduce the count to half of the original value. This half-value thickness is an important concept for absorption of gamma rays at Advanced level. AQA GCSE Science: P1b 6.5 Radioactivity issues AQA Specification Link Substantive content that can be revisited in this spread: • The uses of, and the dangers associated with, each type of nuclear radiation. Students should use their skills, knowledge and understanding of „How Science Works‟: • to evaluate the possible hazards associated with the use of different types of nuclear radiation • to evaluate measures that can be taken to reduce exposure to nuclear radiations • to evaluate the appropriateness of radioactive sources for particular uses, including as tracers, in terms of the type of radiation emitted and their half-lives. Teaching suggestions Activities Nuclear waste – Extensive details of the handling and storage of nuclear waste can be found from the Internet. A basic search for „nuclear waste‟ will yield sites from BNFL, Greenpeace and a range of other pro and anti nuclear organisations. Interestingly the device used to remotely handle dangerous materials is called a „waldo‟. These were thought up by the science fiction author Robert Heinlein, before they were actually turned into reality. Chernobyl – You may have had a debate about Chernobyl and nuclear reactor safety during a previous section. If not, then the students are now better informed and a debate would be very useful. The debate should take into account the need to reduce global warming, the storage of waste produced and the safety record of nuclear power stations. Radioactivity all around us – The students will most likely think of radioactivity being an unnatural phenomenon, and it is important to get across the idea that most of the dose that they receive is from natural sources. You can measure the amount of background radiation during the lesson. Radon gas is a major cause of lung cancer in the UK, with estimates of deaths at around 2500 per year. This compares to about 25 000 due to smoking. The gas is released from igneous rocks; (link back to geothermal energy) and the students may be interested in the areas that contain most of these rocks, such as Devon and Cornwall. Further information can be found from the Health Protection Agency (www.hpa.gov.uk) where radon detectors can be purchased. Shouldn‟t these be free? Radioactivity on the move – This is an excellent opportunity to discuss the safety of radioactive material. Ask the students to list a list of safety precautions that they would impose when moving nuclear material by rail. Search the Internet for „nuclear container test‟ to find video of a nuclear container being tested in a crash. They should also be able to find information about the ships that are used to transport material. How are these designed and protected? ICT link-up In the „Radioactivity on the move‟ or „Nuclear waste‟ activities, the groups can present their evidence as a slide show. This would allow them to use information and images from the Internet easily to support their case. Learning styles Kinaesthetic: Researching further information. Visual: Obtaining and presenting information from the Internet. Auditory: Explaining how radioactive material is kept safe. Interpersonal: Reporting on background radiation. Intrapersonal: Considering safety precautions used when handling materials. AQA GCSE Science: P1b 7.1 How big is the universe? AQA Specification Link • There is a red shift in light observed from most distant galaxies. The further away galaxies are the bigger the red shift. • How the observed red shift provides evidence that the Universe is expanding and supports the „Big Bang‟ theory (that the Universe began from a very small initial point). Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Learning styles • The Universe is a vast Lesson structure Kinaesthetic: Matching spectra cards. collection of billions of Starter Visual: Imagining the expansion of galaxies each containing How many stars? – Give the class estimates on the number of stars in a galaxy the Universe. millions of stars. and the number of galaxies, and ask them to work out how many stars they could Auditory: Explaining the evidence for • The velocity of distant expansion. galaxies can be measured by have each if they shared them out between the class. (5 minutes) (1022 to 1024 Interpersonal: Discussing and analysis of the red shifting of stars in the Universe) evaluating the evidence. light from those galaxies. Our star – Get the students to list the reasons why the Sun is important to life on Earth. What does it Intrapersonal: Appreciating the model • The evidence gained from provide the Earth with? (5–10 minutes) of the expanding Universe. red shift analysis proves that Stars and planets – Give the students sets of cards describing the properties and behaviours of stars and • Gifted and talented the Universe is expanding and planets, and ask them to sort them into two piles. (5–10 minutes) Emission spectra is of finite age. If you have a set of gas emission Main spectrum tubes, you can demonstrate • You might like to ask the students why there are no photographs of the complete Milky Way the emission spectra of different hot Equipment. galaxy; they should realise that we could never get a probe to sufficient distance. gases. With a suitable diffraction Calculators • If you want to show a model galaxy, try using a blank CD with a small bulge of Plasticine in the centre. grating and spectroscope, you can Large balloon You can draw the spiral arms on the label. It‟s about the right proportions (according to NASA). We are clearly see the distinct lines produced on the western spiral arm about 1cm from the rim. by different elements. If you don‟t • You can then show the separation of galaxies. Our neighbour Andromeda would be about 1m away on have a spectroscope, you can still this scale. show the different colours from • A Doppler shift for sound (a similar effect to the red shift) can be demonstrated with a tube and a funnel. different elements. (You may also The students may be familiar with the effect when hearing sirens on cars passing by. wish to link this idea to the flame • It is useful to show the students simple samples of absorption spectra to show what these lines would tests for the applied science units.) look like. They can then show the effect of shifting the lines to the red part of the spectrum. See Attatched • ICT link-up. Why do scientists powerpoint. need more and more powerful • The idea of an expanding universe that has no centre is a bit strange. The closest simple analogy is the computers? Simulations of galaxies surface of an expanding balloon. It is worth showing this: blow up a balloon with galaxies drawn on its smashing together may look nice, but surface and they all move further apart from one another and none of them are in the middle. it takes a lot of computing power to • The Universe is a bit like this; but it isn‟t expanding „into‟ anything as it is expanding in three work out when a billion stars meet dimensions, not two like the surface of the balloon. another billion stars. Many of the If pupils question this explain that the universe is expanding at the speed of light, and since simulations on-line have been carried nothing can move faster it is impossible to catch up with „the edge‟. out by „supercomputers‟ thousands of times more powerful than a simple PC. There is a PhotoPLUS, P1b 7.2 Plenaries „Big bang‟, available on the GCSE Space is big – Give the students a list of distances and ask them to put them in order Science CD. This could be used next (e.g. Earth to Moon, Earth to Sun . . . Milky Way to Andromeda). (5 minutes) lesson. True or false – Give the students a set of „facts‟ about galaxies and the Universe, and ask them to say if they are true or false. (5–10 minutes) Corrections – Give the students a paragraph full of mistakes describing the expansion of the Universe. They must correct every mistake. (5–10 minutes) Learning Outcomes Activities and extensions Most students should be able to: Doppler and sound • State that the Universe contains a vast number of galaxies and stars. A 1.5 m length of hosepipe is ideal for this, but other tubes work reasonably. You • Explain that red shift evidence shows that the Universe is expanding. need to stick a large funnel (firmly) in one end and then blow down the other, while swinging the tube above your head. The pitch (and so frequency and wavelength of Links: the sound) changes as it swings towards and away from the students. When it is moving away, the wavelength is increased so the sound is lower pitched and vice Expanding Universe powerpoint versa. Matching spectra Doppler effect animation: http://www.freezeray.com/flashFiles/DopplerEffect.htm Can the students discover what elements are present in real stellar spectra? Give the And students a card showing the absorption spectrum of the Sun and a set of spectra for http://molebash.com/doppler/home.htm different elements, some of which are present in the Sun; ask the students to work out which ones match. Make sure the cards are printed to the same scale though. Andromeda ascendant The Andromeda galaxy is one of our nearest galactic neighbours and it is getting nearer all the time. It‟s moving towards us at about half a million kilometres per hour and will eventually collide in three to four billion years‟ time. The students could look into the possible outcomes of this collision, and collisions on this scale generally. There are numerous excellent computer simulations, and Hubble Space Telescope images of real collisions, available on the Internet. AQA GCSE Science: P1b 7.2 In the beginning there was nothing...which exploded! AQA Specification Link • How the observed red shift provides evidence that the Universe is expanding and supports the „Big Bang‟ theory (that the Universe began from a very small initial point). Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Gifted and talented. Just how • The Universe is thought to Lesson structure small is „small‟? These students have begun in a dramatic Starter may wish to look into the event called the Big Bang. Bang! – Show a video clip of a large explosion and ask students to describe dramatically what is going on. concept of singularities: objects • The expansion of the (5 minutes) Universe supports the Big Heat death – Remind students that all energy transfers lead to energy being wasted as heat. Ask them to of zero volume and infinite Bang theory. describe what will happen when all of the energy the Universe started with is wasted. (5 minutes) density; it is from one of these • The cosmic microwave Your history – Give the students a list of historical events reaching back through that the Universe is thought to background radiation is a have originated. The ideas are human history, and then to the formation of the Earth. Ask them to put the events primary piece of evidence closely linked to black holes, leading to this conclusion. in order. (15 minutes) which the students will study later in the next topic; you may Main Equipment. • This lesson is all about big ideas and how scientists have to provide evidence for them. (It is ideal for wish to leave this until then and NA teaching aspects of „How Science Works‟.) link the two ideas together. • Many students may ask what was before the Big Bang. The best approach is to talk about the meaning of • Learning styles „before‟. As scientists believe that time only started with the Big Bang there was no time before it, so it is Kinaesthetic: Research into meaningless to ask questions about what happened. A PhotoPLUS, P1b 7.2 „Big bang‟, is available on the previous ideas about the Universe. GCSE Science CD to help students explore the idea. Visual: Imagining the Big Bang. • Students may also be a bit confused by the term „explosion‟. The Big Bang is better described as a sudden Auditory: Hearing the description expansion and the production of a lot of energy. As the Universe continues to expand, this energy gets more of the end of the Universe. and more dissipated and so the Universe cools down. Interpersonal: Discussing the origin • The main thrust of the lesson is to explain to the students that an idea like the Big Bang needs to of the Universe. have evidence before it is accepted by scientists. It is not enough to come up with the best Intrapersonal: Considering the evidence for the Big Bang model. sounding explanations. This links to the „fundamental ideas‟ section of „How Science Works‟. • ICT link-up. There are several • Those that did not accept the theory were right to, until they were given evidence of the cosmic background web sites explaining the Big Bang radiation. They should then accept the new model, or come up with an alternative explanation that takes the and theories about possible ends to new evidence into account. the Universe. Some are a bit • Changes to ideas like this are important to science; the students need to know that scientists will analyse technical, but students may wish to new ideas and accept them if they explain the evidence better than the old ideas. This process ensures that find out more from them. Search at scientific knowledge develops and becomes a better description of the Universe. www.nasa.gov or www.bbc.co.uk. • You should also point out that recent discoveries, such as the possible speeding up of the expansion, will also have to be explained by scientists over the coming years; we do not have a complete description of the Universe and may never have. • Conditions in the very early Universe were very different than they are now. The temperatures were so high that atoms could not exist, and even protons and neutrons could not form. • The cosmic background is a result of this stretching of the wavelength; you can link this to the idea of red shift but the two processes are a bit different. • The end of the Universe is still open to debate, and students should not worry too much about it. We have a few billion years to go before a „Big Crunch‟ or a „Big Yawn‟. Plenaries Better Big Bang – The term „Big Bang‟ is not a very good one to describe the beginning of the Universe. Can the students come up with a better term for it? (5 minutes) Can science answer everything? – Have a brief debate with the students about the limits of scientific understanding. Can all questions be answered by scientific research? (10 minutes) Learning Outcomes Activities and extensions Most students should be able to: A steady state • Describe the Big Bang as the event that generated the Universe. Some scientists heartily resisted the idea of a „Big Bang‟ and expanding Universe. • Describe the evidence for the expansion of the Universe and how it supports the Big Bang The students could find out who these where and what their objections were. Do all theory. scientists agree on the Big Bang model now? • State the evidence for this conclusion. Improving evidence Ever since the discovery of the cosmic microwave background radiation, scientists Some students should also be able to: have been trying to find improved ways of measuring it so that they can find out the • Describe possible scenarios for the destiny of the Universe. structure of the early Universe. The students can find out how satellites, including the COBE mentioned in the Student Book, have been used to map the radiations and find variations in it. There are several satellites that have been used, or are due for launch in the coming years, all with dedicated web sites. AQA GCSE Science: P1b 7.3 Milky way, comets and Pluto. More than a choc, shops and a dog? AQA Specification Link • Observations of the solar system and the galaxies in the Universe can be carried out on the Earth or from space. • Observations are made with telescopes that may detect visible light or other electromagnetic radiations, such as radio waves or X-rays. Students should use their skills, knowledge and understanding of „How Science Works‟: • to compare and contrast the particular advantages and disadvantages of using different types of telescope on Earth and in space to make observations on and deductions about the Universe. Learning Objectives Teaching / Learning activities (including How Science Works) Teaching suggestions Students should learn: • Gifted and talented. What is a • A range of objects can be Lesson structure „black hole‟? The students can find observed from the surface of Starter out about how these are formed and the Earth and from orbit What’s out there? – The students should list all of the different types of object that can be seen in space how they behave. Will black holes around it. from the Earth‟s surface with the naked eye, and perhaps draw what they look like. (5–10 minutes) eat up our entire galaxy one day in • The atmosphere absorbs Astronomical question loop – A chain of questions and answers about objects in the solar system. (5–10 the distant future? some regions of the EM minutes) • Learning styles spectrum and so prevents us Shoddy solar system – Give the students a set of incorrect facts about the solar system Kinaesthetic: Making and using from observing these regions and ask them to correct them. (5 minutes) See Links telescopes. from the surface of the Earth. Visual: Observing astronomical • Satellites above the images. Main atmosphere can be used to Interpersonal: Discussing the • This is a fairly visual topic and benefits a lot from the use of images. Try to find some good detect a larger range of EM advantages of space-based waves, free from atmospheric slides of all of the objects mentioned in the spread to show the students when they come up. telescopes. distortions. There are many good sources of amazing images and animations. (Search at www.nasa.gov or • ICT link-up. Students can view www.bbc.co.uk. the PhotoPLUS, P1b 7.3 „Looking Would help to have textbooks available for this and the following lesson, hence the book box. into space‟ in this lesson. Equipment. • The students should be aware of comets from Key Stage 3. It is interesting to show them some historical incorrect facts wsheet comet events: perhaps the Bayeux tapestry or the Shoemaker Levy 9 and Jupiter collisions. http://www.windows.ucar.edu/tour/link=/comets/comet_model_interactive.html very good site for showing the path of comets, speed and their tails. • There will probably be a discussion about what will happen if a comet or meteor hits the Earth about now. You can deal with this now or in the next spread later; have a look there for more information. • If you are working in a large town or city, some students will not have been able to see the full detail of the Milky Way crossing the sky; it is well worth showing them just how many stars are out there. • Try building the simple telescopes; the students may improve on the basic design. • Link radio telescopes back to their understanding of the electromagnetic spectrum. Discuss that the telescopes have to be very large because radio waves carry a lot less energy than visible light. • When discussing satellites, point out that the main benefit is that they are above the atmosphere. The atmosphere blocks quite a lot of the electromagnetic spectrum, so we would not be able to look at objects that emit in these regions from the Earth‟s surface. Interesting point for discussion about Plutos demotion to being a plannetoid. Possible pro and con argument! Plenaries Jeopardy – Students have to think up questions about a list of astronomical objects and terms. (10 minutes) Comet legends – Comets are often associated with bad luck or major events. Can the students come up with a comet legend about where they come from? (10 minutes) It’s life Jim – Is there life „out there‟? Discuss the sort of things we should be looking for to find evidence of alien life. (5–10 minutes) NB: Next lesson requires a computer room to be booked Learning Outcomes Practical support Most students should be able to: Making astronomical telescopes • List a range of commonly observed space objects and the equipment that is required to see Simple telescopes are easy to build, but fiddly to use. them clearly. Equipment and materials required • Explain why it is not possible to monitor all EM waves from space at the surface of the Metre rulers, 50cm and 5cm focal length converging lenses, some 75 cm lenses, Earth. Plasticine. Details Some students should also be able to: Mount the 5cm lens at one end of the ruler and the 50cm lens 55cm along the ruler • Describe the range of EM waves that can and cannot penetrate the Earth‟s atmosphere. using Plasticine. The students look through the fatter (5cm) eyepiece lens and if they • Describe the types of objects that produce gamma rays and infra-red radiation in space. have aligned the lenses fairly straight, they should see an image. The image should be magnified by a factor of five, but will only show a small part of what the Links: telescope is pointed at. The students should think about how they would be able to get a larger image and think up some ideas about improving magnification. Try the Sol System errors combination of 5cm and 75cm positioned 80cm apart. www.nasa.gov Improving telescopes http://www.bbc.co.uk/science/space/solarsystem/index.shtml Once the students have explored basic telescopes, you could ask them to design www.brainpop.com improved models. Perhaps they could think of sturdier ways of mounting the lenses. Some students may try to think of ways of getting the image the right way up; they could research „terrestrial telescopes‟. Armageddon? Should we be designing anti-comet and anti-asteroid measures? What can be done and would it work? The students could produce a report on the feasibility and usefulness of this idea. They would need to find out about the actual odds of an impact and how much damage it would cause. AQA GCSE Science: P1b 7.4 Looking into the unknown AQA Specification Link Candidates should know and understand: • Observations of the solar system and the galaxies in the Universe can be carried out on the Earth or from space. • Observations are made with telescopes that may detect visible light or other electromagnetic radiations, such as radio waves or X-rays. Students should use their skills, knowledge and understanding of „How Science Works‟: • to compare and contrast the particular advantages and disadvantages of using different types of telescope on Earth and in space, to make observations on and deductions about the Universe. Teaching suggestions Activities I would suggest giving pupils a series of questions that require research on their part to answer. See Webquest in links for examples. A short history of the Universe – The students should be able to find several web sites describing the early stages of the Universe. Many of these will be overly technical, but they should get the general idea that the Universe was very different than it is now: atoms did not exist and light could not travel. The students should extend their timeline into the current era, adding on information about the formation of our solar system and possibly even life on Earth. For what fraction of the life of the Universe has humans existed? Galileo – There are many resources about Galileo Galilei and the students should prepare this information before the trial. You should be able to find transcripts from the trial, the charges, verdict and the recantation of the „heretical‟ ideas by Galileo himself. Mars Blog – The difficulties in getting to Mars in the first place should not be under-estimated. Ask the students to find out what resources would have to be taken for the trip and how long it would take with current technology. They should be able to find a lot of information about the surface of Mars, as several probes have visited recently. Space invaders! – The odds of being killed in an event like an asteroid impact lie between 1 in 20 000 and 1 in 1 000 000 000 000 depending on the information source. This should reassure the students of their safety; although the dinosaurs may disagree. Even though an impact is unlikely, the damage would be tremendous – as the students will be aware of from a range of films and television programmes. Some sources claim that we are „overdue‟ an impact: this is a misunderstanding of statistics that you may wish to correct. The fact that we have not had an impact in a long time does not increase the chance of one occurring next year or the year after. The chance is the same (very small) each year. Some interesting impacts worth talking about are the Chicxulub „Dinosaur killer‟ that hit the Yucatan peninsula 65 million years ago; the Barringer meteor crater in Arizona and the mysterious Tunguska impact. There are many web sites dedicated to meteor impacts. Search at www.nasa.gov or www.bbc.co.uk. SETI – SETI has an interesting web site (www.seti.org) with a great deal of information about their activities. It also has detail of the „Drake Equation‟ mentioned in the „Gifted and talented‟. Extension or homework The students can visit the SETI site at home and may like to become involved with the search by joining the SETI@home project. With this, they can get their home computer to analyse signals and perhaps discover alien life for themselves. ICT link-up Students can analyse the odds of discovering alien life in the Universe with online versions of the Drake equation. Search the Internet for „Drake equation‟. They can change the odds of each of the parameters and see how many intelligent species are predicted to be in our galaxy. Teaching assistant Your teaching assistant can be very helpful in the recording of discussions or helping to generate ideas in group work. They may also be of assistance with the construction of the telescopes. Learning styles Kinaesthetic: Constructing telescopes (if not done in previous lesson). Visual: Imagining life on Mars. Auditory: Explaining their ideas. Interpersonal: Debating the treatment of Galileo. Intrapersonal: Writing a report about asteroid impacts. Gifted and talented These students should discuss the chances of there being intelligent alien life in the Universe and our chances of contacting them. They should list all of the things that are needed by intelligent life, and then look into the Drake equation to find the chances of life being out there. The Drake equation is quite good to model using a spreadsheet.
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