Waves

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

There are two sorts of waves Transverse waves Longitudinal waves

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

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)

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

What do waves do? All waves carry energy

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)

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

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)

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)

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

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

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)

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

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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