2. Waves

3. What are waves? There are many different kinds of wave: Light waves Sound waves Waves on water Seismic waves Waves along a rope, or a slinky

4. There are two sorts of waves Transverse waves Longitudinal waves

5. Transverse waves Most waves are transverse The vibrations in transverse waves go from side to side The energy is travelling in one direction, with the vibrations moving at a 90 o angle to the direction the wave is travelling

6. Transverse Waves After a great performance at a drum and bugle corps contest, the audience decides to start a wave in the stands. Each person rises and sits at just the right time so it looks like a wave. This is a transverse wave because, as the wave moves across the stands, folks are moving up and down. wave direction

7. Longitudinal Waves Longitudinal waves have vibrations moving in the same direction that the wave is travelling in Examples of longitudinal waves are: Sound waves (in solids, liquids and gases) Shock waves (e.g. seismic waves ) A slinky (when plucked )

8. Longitinal Waves (cont.) Ouch ! C C C R R C = Compression (high kid density) R = Rarefaction (low kid density) The compression (the pulse) moves up the line, but each kid keeps his place in line.

9. Examples of different waves Transverse waves: All electromagnetic radiation, e.g. light Ripples on water Waves on strings A slinky that is waved up and down Longitudinal waves: Sound Shock waves A slinky when plucked

10. What do waves do? All waves carry energy

11. What sort of energy is being carried? Heat energy is carried by light, infra red and microwaves X-rays and gamma rays carry energy which can damage cells Sounds carry energy in the form of vibrations. Loud sounds can make an object vibrate (move) Waves on water can move things, and can even be used to generate electrical energy Televisions, radios, fibre optics and speech are all ways in which energy travels (and also information)

12. What does a wave look like? A wave can be drawn as a wavy line:

13. What are the main parts of a wave? Wavelength ( ) Amplitude Frequency (f) This is the distance from the crest of one wave to the crest of the next wave This is the height of a wave from the mid-point (where there is no displacement) to a peak This is the number of complete waves per second, passing a certain point. It is measured in Hertz (Hz)