Electro-magnetic waves can be measured in terms of wavelengths and frequencies. The distance between the top of one wave and the next is called wavelength. The number of waves that radiate from a centre every second is called the frequency. Frequency is measured in cycles per second. A cycle is one backward and forward movement of alternating current ( which makesup electro-magnetic waves ).

High frequency is a lot of cycles per second, low frequency is fewer cycles per second.

Frequency wavelength = speed of light. High frequency goes with short wavelength and low frequency goes with a long wavelength. This is so because electro-magnetic waves travel at the speed of eight.

It is usual to refer low frequencies in terms of wavelengths and high frequencies in terms of frequency.