For further information about EMF, we need to know what frequency is.

The frequency is related to a wave in physics.

The wave can be shown as follows.

Time is usually put on the horizontal axis in such waveform.

Followings is one wave of the waveform.

Frequency is the number of the wave per second and is shown with unit hertz (Hz).

Followings are examples of a wave with various frequencies.

A wave with higher frequency has higher energy.