A wave transfers energy from one place to another without transferring matter. The particles of a medium, or the fields in a light wave, vibrate about a fixed rest position while the energy moves on.
The amplitude of a wave is the maximum displacement of a point on the wave from its rest position. The wavelength is the distance from a point on one wave to the same point on the next wave. The frequency is the number of complete waves passing a point each second, measured in hertz (Hz). The period is the time taken for one complete wave, measured in seconds. Period and frequency are linked by period = 1 ÷ frequency, so a wave with a frequency of 4 Hz has a period of 0.25 s.
A microphone connected to an oscilloscope displays a sound wave as a trace. The height of the trace above the centre line shows the amplitude, and the time for one complete wave along the horizontal axis shows the period. A louder sound gives a larger amplitude. A higher pitched sound gives a higher frequency, so more waves fit across the screen.
