Дата публикации: 2017-10-23 06:49
The frequency , f , of a wave is the number of waves passing a point in a certain time. We normally use a time of one second, so this gives frequency the unit hertz (Hz), since one hertz is equal to one wave per second.
The wavelength , λ , of a wave is the distance from any point on one wave to the same point on the next wave along. (The symbol is a Greek letter, 'lambda'.) To avoid confusion, it is best to measure wavelength from the top of a crest to the top of the next crest, or from the bottom of a trough to the bottom of the next trough. Wavelength is also measured in metres (m) - it is a length after all.
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Don't get confused with this quantity frequency. It is not a distance travelled by waves, nor is it a speed, although it is linked to both of these quantities. For water waves and sound waves the unit hertz is usually good enough but radio and TV waves have such a high frequency that the kilohertz (kHz) or even the megahertz (MHz) are better units.
The amplitude , a , of a wave is the distance from the centre line (or the still position) to the top of a crest or to the bottom of a trough. Be careful with this quantity - the centre line is not always given in a diagram. Amplitude is measured in metres (m). The greater the amplitude of a wave then the more energy it is carrying.
Answer these questions about the waves shown. If you need to, re-run the motion of the waves. Remember to include units where necessary.
The speed (or sometimes you might see it called velocity ) of a wave, v , is how far the wave travels in a certain time.
We also have Bitesize study guides covering many subjects at National 9 and National 5 on our Knowledge & Learning BETA website.
You need to know about these quantities used in waves - what they mean, the symbols used for them and the units used to measure them.