Describing waves

There are some terms required for discussing waves.

Here are some terms associated with periodic waves. The wavelength is the distance from a part of one wave to the same part in the next wave, such as from one crest to the next. The amplitude is the displacement from the rest position. The period is the time required for a wave to repeat itself, that is the time for one complete wavelength to move past a given location.

1. Wavelength the distance between two successive in-phase points; symbol is l and SI unit is meters
2. Amplitude maximum displacement of wave; measure of wave's energy
3. Frequency the number of waves passing a point per second; symbol is n or f and SI unit is Hertz (Hz)
4. Period time for one wave; symbol is T and SI unit is second

T = 1 / n     or     T = 1/f

n = 1 / T     or     f = 1/T

5. Speed the speed with which the wave moves through the medium is the product of the wavelength and the frequency; SI unit is m/s

v = l n     or    v = l f

Sample problem:

The speed of light is 3.0 x 10⁸ m/sec.  The wavelength of red light is 700 nm  or 7x 10 ^–9m  What is the frequency of this wave? 

Frequency is f and wavelength is l.

Answer