INTRODUCTION TO WAVES

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					INTRODUCTION TO WAVES




             What is a Wave?

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        Lesson Overview

• In this lesson, students will learn the
  concepts/terms used in wave propagation.
• Discussion will then focus on the
  classification of waves
• Briefly look at the effects of hole size in
  relation to wavelength in diffraction of
  water waves (An introduction into wave
  properties)

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           Review of Waves
                Wave terminology
1. What are Mechanical Waves? Answer: Mechanical
   Waves are waves which propagate through a
   material medium. A medium is any material that
   allows wave propagation. Examples are solid, liquid
   or gas

2. Give two basic types of wave motions for
   mechanical waves. Answer: longitudinal waves
   and transverse waves

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        NOTE THE DIFFERENCE
• Distinguish between longitudinal and
  transverse waves.
• Answer: In a transverse wave, the motion
  of the medium is perpendicular to the
  motion of the wave.

• In contrast to transverse waves, longitudinal are
  waves in which the medium moves back and
  forth in the same direction as the motion of the
  wave.
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    Examples of Transverse Waves
• Water waves are known as transverse waves obviously
  because the motion of the water is up and down, or at
  right angles to the direction in which the waves are
  travelling.
Other known examples are
• radio waves,
• light waves, and
• heat waves


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  Examples of Longitudinal Waves

• Sound waves are longitudinal waves

• Why is sound wave classified as a
  longitudinal wave?

• This is because sound waves travel back
  and forth in the same direction as the
  wave motion.
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  Sound Wave – A Classic Example

• As a sound wave is propagated and
  moves out of a loud speaker to the ear
  of a listener, particles of air vibrate
  (are disturbed) back and forth in the
  same direction and the opposite direction
  of energy transport.




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Mechanical and Electromagnetic Waves


• What is an electromagnetic waves?
 An electromagnetic wave is a wave which
  is capable of transmitting its energy
  through a vacuum ( a vacuum is an empty
  space).




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 What is a Mechanical Wave?

• A mechanical wave is a wave which is not
  capable of transmitting its energy through a
  vacuum (empty space)
• Mechanical waves require a medium in order
  to transport their energy from one place (the
  source) to another.
• Obviously sound cannot be transmitted in a
  vacuum hence a sound wave is an example
 of a mechanical wave.
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ABOUT DIFFRACTION OF WATER WAVES

• Diffraction is one of the most interesting,
  and also very useful, properties of waves.
• What happens when water wave strikes a
  barrier with a hole?
• A part of the wave can move through the
  hole. Note: The part of the wave that
  strikes the wall will not move forward
• Note: Diffraction can only take place if
 the hole in the barrier is similar in size to
  the wavelength of the wave.
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    ANIMATIONS OF WATER WAVES




•   Log on to the web address shown below to see Diffraction of water wave animation
•   http://www.ngsir.netfirms.com/englishhtm/Diffraction.htm


•   Log on to the web address shown below to see interference of water wave animation
             • http://www.ngsir.netfirms.com/englishhtm/Interference.htm




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    HOMEWORK/ASSESSMENT

• Suggested Student Assessment:
• Ask the students to research the
  characteristics of mechanical waves.
• Distinguish between light waves and
  sound waves
In our next lesson we shall be looking at
  the unique nature and properties of
         different wave types
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