1. Waves

2. 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

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

4. 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 90o angle to the direction the wave is travelling

5. 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)

6. 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

7. What do waves do?
All waves
carry energy

8. 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 cause ionisation and 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)

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

10. What are the main parts of a wave?
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)
Wavelength ()
Amplitude
Frequency (f)

11. Sound waves Sounds are produced by vibrations
Sound travels as longitudinal pressure waves
The frequency of a sound will determine its pitch (how high or low a sound is)

12. Hearing range
Sounds can range from very low frequencies (with a low pitch) to very high frequencies
Humans can only hear a certain range of frequencies (our hearing range)
As we get older our hearing range is reduced, and we do not hear some of the higher frequency sounds anymore

13. High frequency sounds
High frequency sounds have a high pitch, like a mouse squeaking
High frequency sounds have short wavelengths

14. Ultrasound Bats send out very high-pitched squeaks This is ultrasound
Ultrasound will reflect off objects in its path
Bats can detect this and use the information to know if something is in their way, and to fly around it (or to catch it if it’s a moth)

15. How can we use ultrasound?
Hospitals use ultrasound scans to examine unborn babies in the womb
As the ultrasound waves hit the foetus, some is reflected, and a computer converts this into an image
Ultrasound waves are safer than X-rays, which can harm a foetus

16. Another use for ultrasound waves:
Sonar uses high frequency sound waves which reflect off the sea bed, or off shoals of fish
Reflected sound waves coming back are detected
Information obtained in this way can tell us about the features of the sea-bed, the depth of the water, or whether there is a shoal of fish nearby.

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