The Wave Equation

There are three properties of a wave that we need to recognise

Wavelength
This is the distance from crest to crest. It is measured in metres (m)

Frequency
This is the number of waves which pass a point every second. It is measured in Hertz (Hz)

Speed
This is how fast the wave is travelling. All electromagnetic waves travel at the same speed in space. It is 300,000,000 m/s ( 3 x 10⁸ m/s )
( This is VERY fast. In fact, according to Albert Einstein, nothing can travel faster.)

These three quantities are related by the equation speed = frequency x wavelength

As different electromagnetic waves have the same speed then they have different frequencies and wavelengths.

The larger the wavelength of the wave, the smaller its frequency.

Radio waves have the biggest wavelength and the lowest frequencies.

Gamma waves have the smallest wavelengths and the highest frequencies.

You will have to use the equation above to calculate either the speed, frequency or wavelength of an electromagnetic wave.

Examples

Calculate the wavelength of Century Radio which transmits at a frequency of 100.7 MHz (million Hertz)

s = f x w so w = s / f = 300,000,000 / 100,700,000 = 2.98m

Microwaves used to heat food have a wavelength of 12.24cm (0.1224m). calculate their frequency.

s = f x w so f = s / w = 300,000,000 / 0.1224 = 2.45 GHz (billion Hz)