Thermometers

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					Health Physics
Standard Grade Physics
  Dumfries High School
  Thermometers                  Diagnosis                       Ultrasound          Stethoscope


                                                                                                  Noise
                      Temperature                                       Sound                     Level



               Detection

Radiation types            Shielding                                                       Refraction

                                              Health
    Nuclear Radiation                                                         Light & Sight
                                              Physics
  Ionisation           Activity (Bq)
                                                                                Eyesight           Lenses

       Absorbed dose (Gy)

                                                                              Long/Short
      Dose Equivalent (Sv)                    EM Spectrum                                           P= 1/f
                                                                                 Sight

               Half Life
                                       Visible Light           X-rays

                                   Infrared      Ultraviolet     Gamma Rays
                                                                                           Sunday, 14 August 2011
Thermometers
Standard Grade Physics
         Health Physics
     True or false
In pairs, try to answer the following questions as either true
    or false.

1.    Normal human body temperature is about
      36-37 °C.
2.    Humans can survive with a body temperature of between
      31 and 47°C
3.    A fever is caused when the body thinks it is too cold.
4.    Sweating is the body‟s response to being too warm.




                                                        Sunday, 14 August 2011
 Thermometers
All types of thermometer make use of a
  measurable property which changes with
  temperature.

For example
Mercury and alcohol expand when heated and
  contract when cooled.
Digital thermometers make use of temperature
  dependant resistors in which the resistance
  changes with temperature.


                                           Sunday, 14 August 2011
 Thermometers


  Thermometer         Advantage        Disadvantage

Digital thermometer Quick             Expensive

                   Simple & hard to
Bimetallic Strip                      Inaccurate
                   break
Forehead
                   Easy to use        Not accurate
Thermometer
Alcohol (lab)      Large range,
                                      Not precise
thermometer        versatile
Clinical
                   Very accurate      Small range.
Thermometer                                         Sunday, 14 August 2011
Liquid in glass thermometers

Copy & label the diagram opposite then answer
   the questions below in sentences.

1.   How does a liquid in glass thermometer
     work?
2.   What are the differences between a normal
     alcohol thermometer and a clinical
     thermometer?
3.   Why is there a kink in the inside tube of a
     clinical thermometer?
4.   Describe how to measure body
     temperature using a clinical thermometer.
                                                   Sunday, 14 August 2011
 Temperature and Diagnosis
Measuring a patient‟s temperature can help to
 diagnose their condition and the severity of it.

If they are too hot (have a fever) then the body is
   probably fighting an infection or virus. This is
   called hyperthermia.

If they are too cold it is often a sign that the patient
   is exhausted and their body cannot maintain its
   temperature. This is called hypothermia.

                                                Sunday, 14 August 2011
             Sound
Standard Grade Physics
         Health Physics
 Sound Transmission
Unlike light, sound requires something to travel
 through. Sound can travel through solids liquids
 and gases, but cannot travel in a vacuum like
 space.
Generally, sounds travel faster through denser
 materials.
Speed of sound in air       = 340 m/s
Speed of sound in water = 1500 m/s
Speed of sound in steel     = 5960 m/s



                                          Sunday, 14 August 2011
  The Stethoscope


  Doctors use stethoscopes to listen to the heart and
     lungs inside your body.
  In a stethoscope, all the sound produced at the
     diaphragm end is transmitted up the tube to the
     earpieces. Very little is lost along the way so the
     doctor hears a much louder sound.

  Sound Tubes


Diaphragm
                                                Ear Pieces
                                                     Sunday, 14 August 2011
    Measuring Heart Rate using a stethoscope

   Put the ear pieces in your ears.
   Place the diaphragm either directly onto your skin or
    through a thin shirt just left of where your rib cage meets
    on your front.
   Count the number of beats you hear in one minute. Use
    a friend to help you time it.

   Copy & Complete the following sentence
    Using a stethoscope my rest heart rate was
    measured to be ________ beats per minute.



                                                      Sunday, 14 August 2011
 Ultrasound
Humans can only hear sounds between
 approximately 20Hz and 20,000Hz, however,
 sounds out with this range do exist. My own
 range of hearing is _____Hz to _______Hz

Sounds with frequencies above the range of
 human hearing (above 20,000Hz) are called
 ultrasounds.




                                        Sunday, 14 August 2011
 Ultrasound in medicine
In medicine, ultrasound can be used as an
  alternative to X-rays to look inside the body. The
  advantage is that ultrasound is completely
  harmless.
For this reason it is
  commonly used to
  examine unborn
  babies.




                                            Sunday, 14 August 2011
 Noise Level
Noise level is measured in decibels (dB) which is a
  very odd scale. For each 10dB increase the
  sound get ten times as loud.
That means a 60dB noise is actually 1000 times as
  loud as a 30dB noise (not twice as loud like you
  might expect!)

  50 decibels   10 times louder     60 decibels

  50 decibels   100 times quieter   30 decibels

  50 decibels   1000 times louder   80 decibels

  90 decibels   1000 times louder   120 decibels

                                                   Sunday, 14 August 2011
    Noise Level Examples
    On scrap paper, in pairs, put these sounds in
     order from quietest to loudest.



     Quiet country lane              Heavy goods vehicle from pavement

     Boiling electric kettle at 2m   Pneumatic Drill at 5m

     Normal conversation at 1m       Alarm clock at 0.5m

     Vacuum cleaner at 3m            Residential Area at night
                                      Nightclub at 3m from speaker




                                                                   Sunday, 14 August 2011
 Noise Level Examples

• 10 dB
• 20 dB     Quiet country lane
• 30 dB
• 40 dB     Residential Area at night
• 50 dB     Boiling electric kettle at 2m
• 60 dB     Normal conversation at 1m
                                             Sounds above 90dB for
• 70 dB     Vacuum cleaner at 3m            long periods will damage
• 80 dB                                      your hearing
            Alarm clock at 0.5m
• 90 dB     Heavy goods vehicle from pavement
• 100 dB    Pneumatic Drill at 5m           Dangerous sound level
• 110 dB    Nightclub at 3m from speaker
                                                           Sunday, 14 August 2011
 Noise Pollution
Noise pollution is any loud noise that people do not
 want to hear.

Common examples include:




                                            Sunday, 14 August 2011
       Refraction
Standard Grade Physics
         Health Physics
       Refraction
When light travels from one material or medium to
  another it changes speed.
This is called refraction.

This is often accompanied by a change in direction
  of the light.




                                           Sunday, 14 August 2011
    Setting up a ray box…
   You will need.
       A ray box
       A power pack (12 V)
       Ray slits
       Your jotter or a sheet of white paper


   Plug in the power pack and connect the ray box.
   Insert ray slits and place the whole thing on top of the
    paper.




                                                      Sunday, 14 August 2011
Experiment

We are going to investigate the path of a ray of light
 as it passes through a rectangular glass block.




Set up this experiment and complete the diagram to
  show the path of the light through and out the other
  side of the block.
                                                  Sunday, 14 August 2011
Refraction

Normal lines are
 always drawn at
 right angles to
 the surface

Draw in and label
  normal lines at
  both surfaces
  where the light
  passes through

                    Sunday, 14 August 2011
 Naming the angles
When drawing ray diagrams….
Always draw a normal and measure your angles
  from it!!




        Angle of
        incidence
                             normal
                                       Angle of
                                       refraction


            air                       glass
                                                    Sunday, 14 August 2011
 Copy and complete
A Normal line is drawn at ____ to the surface
  through which light passes or bounces off.
All other angles are measured from this line.
As light goes from air to glass it bends _______
  the normal.
As light goes from glass to air it bends _______
  the normal.




                                            Sunday, 14 August 2011
            Lenses
Standard Grade Physics
         Health Physics
  Convex Lens

                                      Focal length




                                                 Focal point


A convex (or converging) lens will direct parallel beams of light to
a single point called the focal point.
The distance between the focal point and the lens is called the
focal length.
“fatter” lenses are more powerful and focus the light closer to the
lens, so the focal length is shorter.                    Sunday, 14 August 2011
  Concave Lens
                          Focal length




                       Imaginary
                       Focal point

A concave (or diverging) lens will cause parallel beams
of light to spread out. They will never meet.
If we trace the rays back, the lines meet at an “imaginary
focal point”. The focal length is measured from the lens
to this point but will have a NEGATIVE value.    Sunday, 14 August 2011
 Measuring focal length
The simplest way to measure the focal length of a
  convex lens is this:
                              Focal length

Light
from
distant
                                             screen
source


Using light from a distant source (the sun is ideal)
  form a sharp image on a white surface. The
  image will be upside down and laterally
  inverted.
The distance between the lens and the screen is
  the focal length.
                                                 Sunday, 14 August 2011
 Lens Power
Lens power is measured in Dioptres (D). It is a function of
  the focal length only.




                       1
                    P=
  Lens Power
  (Dioptres)
                       f                 Focal Length
                                         (Metres)

Convex lenses have a positive power
Concave lenses have a negative power


                                                        Sunday, 14 August 2011
     Try these
1.    A lens has a focal length of 0.5m calculate its power.
2.    A lens has a focal length of 20cm, calculate its power.
3.    Find the focal length of a lens of power +3 D.
4.    The distance from the lens system in the eye to the
      retina is 3cm. What would the power of this lens system
      be when the eye is focused on a distant object?
5.    A boy wears glasses. He is said to be -3 in his right eye
      and -2 in his left. Calculate the focal lengths of each of
      the lenses. Are the lenses convex or concave?


Extension: Purple textbook p64-65 Q1-8 “Power of a Lens”
                                                        Sunday, 14 August 2011
Sight & The Eye
Standard Grade Physics
         Health Physics
Eyesight Test


                           A
                        D G
                       H Y W

                  P Q I O G L I

               M K R U Z S K L S E A B


           O R T H D Q J O L M B V X N U K T C M




                                                   Sunday, 14 August 2011
Eyesight and the brain




                         Sunday, 14 August 2011
How the eye works

A lens at the front of the eye focuses an image onto the
  retina at the back in the same way as an image can be
  produced on a screen. The lens can change shape,
  which changes the focal length.

It is this ability that allows
    us to focus on things
    that are close and on
    distant objects.




                                               Sunday, 14 August 2011
How the Eye Works




                    Sunday, 14 August 2011
How the Eye Works




                    Sunday, 14 August 2011
20-20 Vision




Light from a distant
object




Light comes in
parallel from distant
objects




                        Sunday, 14 August 2011
20-20 Vision




Light from a nearby
object




The lens in the eye
gets thicker to allow
us to focus on the
object



                        Sunday, 14 August 2011
Long Sighted




Light from a distant
object




Distant objects are
seen clearly by a
long sighted person




                       Sunday, 14 August 2011
Long Sighted




Light from a nearby
object



Would focus behind
the retina so looks
blurred




                      Sunday, 14 August 2011
Long Sighted



Light from a
nearby object




 Long sight is
 corrected using a
 convex lens




                     Sunday, 14 August 2011
Short Sighted




Light from a
nearby object




 Nearby objects can
 be seen clearly by a
 short sighted person




                        Sunday, 14 August 2011
Short Sighted




Light from a distant
object




 Focuses before it
 reaches the retina
 so looks blurred




                       Sunday, 14 August 2011
Short Sighted



Light from a distant
object




 Short sight is
 corrected using a
 concave lens




                       Sunday, 14 August 2011
Long Sight




Light from a nearby
object                Light from a
                      distant object


Would focus behind
the retina so looks
blurred




                                       Sunday, 14 August 2011
 Eye Defects Summary
Some people need glasses to correct their vision.
  They are either:
Long Sighted
That is, they can see _______ objects but have
                           distant
  trouble focusing on _______ objects like _____.
                           nearby               books
  Long sight is corrected using a _______ lens.
                                    convex

Short Sighted
That is, they can see _______ objects but have
                           nearby
  difficulty seeing _______ objects like _______.
                      distant               scenery
  Short sight is corrected using a _______ lens.
                                    concave



nearby    distant   convex   concave   books    scenery
                                               Sunday, 14 August 2011
The EM Spectrum
  Standard Grade Physics
           Health Physics
The Electromagnetic Spectrum
The EM spectrum comprises all the wavelengths of
  electromagnetic waves. Many of these have
  useful properties and can be used in medicine for
  a variety of purposes. We will look at;

Infra Red
Visible Light
                 Increasing frequency
Ultra Violet
                 Decreasing Wavelength
X-Rays


All Electromagnetic waves move at 3x108 m/s in air.
                                             Sunday, 14 August 2011
    Visible Light
Standard Grade Physics
         Health Physics
 Visible Light
Visible light is the only part of
  the EM spectrum our eyes
  can detect. Lasers are
  usually visible light.
Visible light has a _______
  frequency and _______
  wavelength then infra red.




                                    Sunday, 14 August 2011
 Lasers
Describe in your own words the difference
 between the light from a laser and the light from
 a bulb or fluorescent tube.

Hint:
Does it light a room?
Does the light spread out?
What colour is the light?



                                            Sunday, 14 August 2011
  Lasers
In medicine lasers can be used for:
 Corrective eye surgery
 Cosmetic hair removal
 Tattoo removal
 Burning away tumours (using an endoscope)
 Laser scalpel


In other industries, lasers are used for:
 Security alert systems
 Sniper rifle targeting
 Laser guided weapons
 Laser cutting & welding



                                              Sunday, 14 August 2011
The Endoscope


Visible light can be sent down optical fibres.
  These fibres transmit just the visible light, not
  the heat from a light source. This is often
  called “cold light”.

Copy and complete the diagram below to show
 how light travels through an optical fibre.



                                              Sunday, 14 August 2011
   The Endoscope
Endoscopes use two bundles of fibre to allow a doctor to
  see inside the body without major surgery.


camera


Light from inside the body
is transmitted up another
bundle of fibres to a
camera so the doctor can
see the image.
                             Light from the light source
                             is transmitted up one
                             bundle of fibres to act like
                             a torch inside the body.
         Light               This is called cold light as
         source              no heat is transmitted.

                                                            Sunday, 14 August 2011
Infrared Radiation
  Standard Grade Physics
           Health Physics
 Infrared
Infrared radiation has a
  wavelength just longer than
  light. It is invisible, and
  usually associated with heat
  as it is given off by anything
  warm.

Infrared has wavelengths of
  between 750nm and 1mm.

Calculate the range of
 frequencies for infrared
                                   Sunday, 14 August 2011
Night Vision and then some….


          Outside medicine, IR is
               used in thermal
                  imaging.
          This concept is used in
            both engineering and
                the military.



                                    Sunday, 14 August 2011
What about Medical Uses?
   An infra Red scan or
    “thermograph” of a patient
    provides information on
    circulation and blood flow.
    Thermograph images can
    also be used to locate
    tumours which are warmer
    than surrounding tissue.
    Hot areas show up yellow
    and white, while colder
    areas show up blue.
                                  Sunday, 14 August 2011
    IR in treatment
   IR lamps are also used in
    medicine. They are used
    to treat painful or
    damaged muscles and
    are very common in
    sports medicine to speed
    healing.




                                Sunday, 14 August 2011
     Questions….in sentences…
1.    Describe how IR radiation is used in medical
      diagnosis.
2.    In a thermograph picture, what colour usually
      represents hot areas?
3.    Describe how IR lamps are used to treat
      injuries.
4.    Describe how IR is used outside the medical
      profession.




                                              Sunday, 14 August 2011
     Starter questions (back of jotter)
1.    State one type of thermometer and give an advantage
      and disadvantage for its use.
2.    State the units of frequency and sound level.
3.    State the range of human hearing.
4.    Describe how sounds above the range of human
      hearing can be used in a medical application.
5.    What does it mean if someone is long sighted?
6.    A lens of power 5D is required to correct their vision.
      What is the focal length of this lens?
7.    Describe two uses of infrared radiation, one medical
      and one non-medical.
8.    An infrared wave has a wavelength of 15x10-6m.
      Calculate its frequency.
 1       2     3     4      5     6      7     8     9             10
                                                     Sunday, 14 August 2011
Ultraviolet Radiation
     Standard Grade Physics
              Health Physics
Ultra Violet

Ultraviolet radiation has a slightly
  shorter wavelength than
  visible light. It is a part of
  sunlight but most of it is
  blocked by the atmosphere.
  UV radiation is what causes
  sunburn.

Ultraviolet has wavelengths of
  between 10nm and 750nm.

Calculate the range of
  frequencies for ultraviolet
                                       Sunday, 14 August 2011
We need UV….


    UV radiation is something the human body
     needs. We use it to produce vitamin D3.
    UV is also the part of sunlight which gives us a
     suntan.




                                                 Sunday, 14 August 2011
    But too much…..
   Too much UV can cause sunburn, blistering and even
    skin cancer.




“What's the strongest after-sun you sell?”      Sunday, 14 August 2011
 And we use this how…..?
Believe it or not, UV is very useful.
Strong UV will burn us, but will also kill bacteria and
  viruses. High strength UV radiation is often used
  to sterilise instruments in hospitals.
Low strength UV can be used to treat some skin
  conditions such as acne or psoriasis.




                                                Sunday, 14 August 2011
     Questions….in sentences…
1.    Why does the human body need some UV
      radiation?
2.    What happens when our skin absorbs too
      much UV radiation?
3.    What sort of medical conditions can UV be
      used to treat?
4.    What else can UV radiation be used for? Give
      2 medical uses and one non-medical use.




                                            Sunday, 14 August 2011
Too much UV??




                Sunday, 14 August 2011
X-Ray Radiation
Standard Grade Physics
         Health Physics
X-Rays

X-rays have a slightly shorter
  wavelength (higher frequency)
  than UV. They are most famous
  for being used to take X-ray
  photographs to examine bones.
Too much exposure to X-ray
  radiation is harmful to humans.


 X-rays have wavelengths smaller than 10nm.
 Calculate the minimum frequency of X-rays

                                              Sunday, 14 August 2011
    X-Ray Pictures
   X-rays are not normally present in the environment. They
    can however be artificially created.
   Unlike light, X-rays can pass through many materials,
    including skin muscles and soft tissues.
   X-rays are however absorbed by more dense materials,
    like metal and bone.

With this in mind, examine the X-ray pictures and answer the
   following questions in sentences:
1. When X-rays strike photographic film, does the film
   darken or lighten?
2. How will a break in a bone appear on an x-ray
   photograph?
3. Why could an X-ray photo not be used to examine heart
   or lung function, or look for tumours?

                                                    Sunday, 14 August 2011
X-Ray Pictures


                     Dense Bone




   X-Ray
   Source



                              Photographic
       Soft Tissue            Plate
                                             Sunday, 14 August 2011
Diagnosis with X-rays




                        Sunday, 14 August 2011
 What are the dangers?
X-ray radiation is dangerous and harmful to
  humans in large doses. Radiographers and
  others who work with X-ray machines usually
  leave the room when the X-ray picture is being
  taken.
For the same reason X-ray pictures are never
  taken of pregnant women. If they were, the baby
  could be harmed. Ultrasound scans are used
  instead.



                                          Sunday, 14 August 2011
 CAT Scans
Computer aided tomography scans (CAT scans) also use
  X-ray radiation. They collate the information from many
  conventional X-ray pictures taken from different angles
  to produce a picture of a slice through the body. This
  would not be possible with conventional X-ray
  techniques. These slices can be built up into a 3D
  image. They are much more sensitive than normal X-
  ray photography, but result in a higher dose of
  dangerous X-rays to the patient




                                                 Sunday, 14 August 2011
  Gamma Rays
Standard Grade Physics
         Health Physics
Gamma Rays


Gamma Rays are a type of
 nuclear radiation given out
 by radioactive materials.
 They can pass through
 tissue and bone, and are
 harmful to humans.
Exposure to large doses of
 gamma rays will kill cells.


                               Sunday, 14 August 2011
 Radiotherapy (Chemotherapy)
In chemotherapy, gamma rays
   are sent through the patients
   body with the aim of killing
   cancerous cells.                                   Gamma ray source
   Unfortunately there is always
   some damage to healthy                                                   Target area with
                                                                            tumour at centre
   tissue surrounding the
   tumour.
Chemotherapy can weaken the
   immune system and cause
   hair loss.
To minimise the damage to
   healthy tissues, the gamma
   rays are directed into the      Most damage
                                                                     Some damage
                                                                     done here to
   body from different angles.     done here, kills                  healthy issue
                                   tumour



                                                                         Sunday, 14 August 2011
Radioactive Tracers

While CAT scans and even
  traditional X-rays can be
  used to examine organs,
  they cannot examine their
  function. Radioactive
  tracers can be used for this
  purpose.
Radioactive drugs are
  injected into the body and
  carried through the blood
  and organs. By tracking
  the location of these drugs
  in the body the function of
  the heart, liver, kidneys etc
  can be tracked.
                                  Sunday, 14 August 2011
Detecting Radiation –
Scintillation Counters (Gamma Cameras)
Scintillation counters make use of a special type of crystal
  which gives off a tiny flash of light when it is hit by
  gamma radiation.
These flashes are amplified and can be used to build up a
  picture of where radiation is coming from.
Scintillation counters are used together with radioactive
  tracers to examine the function of organs in the body.




                                                   Sunday, 14 August 2011
     Questions (in sentences please)
1.    What medical condition is chemotherapy used
      to treat?
2.    Describe how chemotherapy is used?
3.    What is meant by the term “radioactive tracer”?
4.    What are tracers like this used for in medicine?
5.    What are the risks of chemotherapy and
      radioactive tracers?




                                               Sunday, 14 August 2011
Nuclear Radiation
  Standard Grade Physics
           Health Physics
Atomic Structure


Protons
Have a positive charge
Are found in the nucleus

Neutrons
Have no charge
Are found in the nucleus

Electrons
Have a negative charge
Are very small and usually orbit
   the nucleus

α                                  β                 γ
                                       Sunday, 14 August 2011
 Nuclear Radiation
All types of nuclear
   radiation come from
   inside an unstable          Alpha
   nucleus. By emitting        Radiation
   the radiation the
   nucleus becomes
   more stable. There          Beta
                               Radiation
   are three main types
   of nuclear radiation.

                               Gamma
                               Radiation



α                          β                  γ
                                Sunday, 14 August 2011
Radiation & Its Properties

    Radiation and its Properties
    Nuclear radiation consists of three types
    Alpha particles ()
                                       two protons and two neutrons.
       These consist of __________________________________________________
                             positively                               large
       Alpha particles are _____________ charged and are relatively __________ in size.
        10 cm
       ________ of air will absorb alpha particles.

    Beta Particles ()
                              electron
       These consist of an _______________ which comes from the break up of a neutron
       in the nucleus.
                             negatively                                small
       Beta particles are ______________ charged and are relatively ____________ in size.
        10m
       ________ of air will absorb beta particles.
    Gamma Rays ()
       Gamma rays consist of electromagnetic radiation.
                       no                                no
       They have ___________ charge and also have ____________ mass.
       Gamma rays are not significantly absorbed by air.



α                                     β                                                  γ
                                                                           Sunday, 14 August 2011
Radiation & Its Properties
    Radiation and its Properties
    Nuclear radiation consists of three types
    Alpha particles ()
       These consist of __________________________________________________
       Alpha particles are _____________ charged and are relatively __________ in size.
       ________ of air will absorb alpha particles.

    Beta Particles ()
       These consist of an _______________ which comes from the break up of a neutron
       in the nucleus.
       Beta particles are ______________ charged and are relatively ____________ in
       size.
       ________ of air will absorb beta particles.
    Gamma Rays ()
       Gamma rays consist of electromagnetic radiation.
       They have ___________ charge and also have ____________ mass.
       Gamma rays are not significantly absorbed by air.

α                                       β                                             γ
                                                                        Sunday, 14 August 2011
    Radiation Absorbtion

                   Radiation can be absorbed by material, but
                      some types of radiation require more
                      shielding than others.

α                  Alpha particles ()
                      Alpha radiation can be absorbed by
β                       a sheet of paper
                      ____________________
                   Beta Particles ()
γ                     Beta radiation can be absorbed by
                        3mm of aluminium
                      ____________________
                   Gamma Rays ()
                      Gamma radiation can be absorbed by
                        at least 3cm of lead
                      ____________________



α                  β                                             γ
                                                   Sunday, 14 August 2011
Detecting Radiation
    Standard Grade Physics
             Health Physics
 Ionisation – The effect of Radiation
Normal atoms have the same number of protons as they
  have electrons. When affected by radiation one of the
  electrons in the atom can be removed. This makes the
  atom positively changed. This process is called
  ionisation.
Alpha radiation causes the most ionisation, followed by
  beta radiation and then gamma which caused the least
  ionisation of the three. X-rays and UV also cause some
  ionisation. These types of radiation are collectively
  known as ionising radiation.


                                             8 electrons
                                             7
                                             8 protons
                                                     positive
                                             Overall neutral


                                                 Sunday, 14 August 2011
 Ionisation – The effect of Radiation
Normal atoms have the same number of protons as they
  have electrons. When affected by radiation one of the
  electrons in the atom can be removed. This makes the
  atom positively changed. This process is called
  ionisation.
Alpha radiation causes the most ionisation, followed by
  beta radiation and then gamma which caused the least
  ionisation of the three. X-rays and UV also cause some
  ionisation. These types of radiation are collectively
  known as ionising radiation.


                                             8 electrons
                                             7
                                             8 protons
                                                     positive
                                             Overall neutral


                                                 Sunday, 14 August 2011
 Biology & Radiation
All living tissue is made up
  from DNA. If the atoms
  in DNA are ionised by
  radiation the DNA is
  damaged.
This can sometimes result
  in the tissue being killed,
  but sometimes can
  cause it to mutate
  causing cancerous
  tumours.
                                Sunday, 14 August 2011
 Detecting Radiation –
 The Geiger Muller Tube
The Geiger-Muller tube (GM Tube) is the most well known
  radiation detector which clicks each time it detects
  ionisation occurring. It is fairly complex, and expensive
  but gives instant and easily understandable results.




                                                   Sunday, 14 August 2011
 Detecting Radiation –
  Film Badges
Film badges make use of the fact that all types of nuclear
   radiation cause photographic film to “fog”. People who
   work in an environment where they might be exposed to
   radiation (eg a nuclear power station) wear these
   badges at all time.
Each month or week (depending on the use) the film is
   checked.
Film badges are very cheap and light, but don‟t give
   instant results. They are good for long term monitoring
   of low level exposure.




                                                  Sunday, 14 August 2011
Detecting Radiation –
Film Badges




                        Sunday, 14 August 2011
Detecting Radiation –
Scintillation Counters (Gamma Cameras)
Scintillation counters make use of a special type of crystal
  which gives off a tiny flash of light when it is hit by
  gamma radiation.
These flashes are amplified and can be used to build up a
  picture of where radiation is coming from.
Scintillation counters are used together with radioactive
  tracers to examine the function of organs in the body.




                                                   Sunday, 14 August 2011
Ionisation and detectors
                Questions – Answer in sentences

1.       Explain what is meant by the term ionisation.
2.       Which type of radiation causes most ionisation and
         which causes least?
3.       Describe the effects of ionisation on living tissue.
4.       For each of the radiation detectors below, describe
         how it works and give one advantage and one
         disadvantage of the detector.
         Film Badges
         Geiger Muller Tubes
         Scintillation counters



 1          2      3       4       5   6     7    8     9             10
                                                        Sunday, 14 August 2011
Analysing Radiation
    Standard Grade Physics
             Health Physics
 Activity
We can measure the activity (A) of a source by
 measuring the number of atoms which decay
 every second. If one atom decays every
 second, the source is said to have an activity of
 1 Becquerel (Bq). This is a very small activity
 and so we usually use kBq or MBq when
 describing sources. The activity of a source will
 decrease over time as more of the atoms decay.

An indication of activity can also be measured
 using a Geiger Muller tube in counts per
 minute
                                            Sunday, 14 August 2011
     Questions
1.    A 1g source of polonium 210 tested and it is found that
      500,000 atoms decay every 4 minute. Calculate the
      activity of the source at this time.
2.    A sample of Uranium has an activity of 60kBq. How
      many atoms decay each hour?
3.    A highly radioactive sample of Protactinium-234
      contains 50x1012 atoms. Half of these decay in a time
      of 7 hours. Calculate the average activity over this
      time period.
4.    The same sample is allowed to continue to decay. Of
      the 25x1012 radioactive atoms remaining, half decay
      during the next 7 hour period. Calculate the activity 14
      hours and 28 hours into the experiment assuming this
      trend continues.
                                                     Sunday, 14 August 2011
Radioactive Half Life
     Standard Grade Physics
              Health Physics
    Half Life Simulation Experiment
Aim
To simulate the principles of radioactive half life.

Method
Each pin represents an atom. We start with 100 „radioactive atoms‟.
Each throw of the pins represents a period of time. If a pin lands with the
  point up it has „decayed‟ and is removed from future throws.
Each throw the number of atoms which decay is recorded.
                                                       Now Graph the class results
Results
                                              decays
Throw   Atoms Decayed    Atoms Decayed
           (group)        (whole class)
1                                                                         throw

2                                                      Conclusion
3                                                      The number of atoms decaying per
                                                       throw decreased as the experiment
4
                                                       progressed. Eventually all atoms
5                                                      would decay and no more radiation
                                                       would be given off.
Your table should allow for up to 12 throws
                                                                              Sunday, 14 August 2011
     Radioactive Half Life
Half life is the amount of time taken for half the radioactive
  atoms in a source to decay. This is the same amount of
  time as it takes for the activity of the source to half.
Questions:
1. A source had an activity of 24MBq three days ago. It‟s half life is
   1 day. Calculate the activity of the source today.

2.    A source had an activity of 800kBq 72 hours ago. Its activity has
      now reduced to 100kBq. Calculate its half life.

3.    A chemical sample was found to have an activity of 8MBq. It
      was purchased 10 years ago. It is marked as having a half life
      of 2 years. What was the original activity of the sample?

                                                             Sunday, 14 August 2011
    Dosimetry
Dosimetry is the study of how nuclear radiation affects the human
  body. We use two different measures of this.

Absorbed Dose
This is the amount of energy in the radiation absorbed by the body, per
   kilogram of mass.

                                         Energy (J)
                   Absorbed dose (Gy)=
                                         Mass (kg)

Equivalent Dose
This is the absorbed dose multiplied by a weighting factor dependant
   on the type of radiation. More damaging radiations have a bigger
   weighting factor.

              Equivalent Dose (Sv) = Wf x Absorbed Dose
.

                                                              Sunday, 14 August 2011
            Well Done
End of Health Physics
     Standard Grade Physics
              Health Physics

				
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