A level revision

Phasors

Phasors describe the displacement in a wave and the direction of this displacement. They consist of a circle, with a circumference of the wave length of the wave, with an arrow which rotates anticlockwise at the frequency of the wave. The arrow points in the direction of the displacement of the wave at that point in time. An simple example of a phasor with the constituent parts:

The phasor shows us the phase of a wave at any point in time, the phase difference between two waves is simply the difference between the phases of each waves phasors when they meet.

Phasors can be added just like vectors: If two waves meet and both their phasor arrows are point directly upwards (i.e. maximum positive amplitude) the resultant wave will be the height of the two waves combined. Like vectors, waves have a direction and so if two waves moving in opposite directions meet their phasor arrows are in opposite directions and so they cancel each other out.

The idea of phasors can be used to explain effects such as superposition and interference