Wave superposition

Superposition is when two or more waves ‘overlap’ in the same place at the same time.

The amplitude of the resulting wave changes depending on the amplitudes of the individual waves and how they line up with each other.

Calculating superposition

The amplitude of the resulting wave can be calculated by adding the amplitudes of the individual waves together.

This is the principle of superposition.

For example, if two waves with amplitudes of 3 cm and 5 cm overlap, the resulting wave will have an amplitude of 8 cm (because ).

Supercrests

A supercrest is formed when two or more crests meet.

It results in a wave that has a much higher amplitude than the individual waves, because the amplitudes of the individual waves add together.

For example, if two waves with amplitudes of 4 cm and 6 cm meet at their crests, the resulting wave will have an amplitude of 10 cm (because ).

Supertroughs

A supertrough is the opposite - it’s formed when two or more troughs meet.

This results in a wave that has a very low (negative) amplitude, because the amplitudes of the individual waves add together in the negative direction.

You can explain this with an example: if two waves with amplitudes of -3 cm and -7 cm meet at their troughs, the resulting wave will have an amplitude of -10 cm (because ).

Minimums

A minimum is formed when a crest and a trough meet. Because one of the waves has a positive amplitude (the crest) at that point, but the other one has a negative amplitude (the trough), the amplitudes will cancel each other out to some extent.

For example, if a wave with an amplitude of 5 cm meets a wave with an amplitude of -3 cm, the resulting wave will have an amplitude of 2 cm (because ).

If the crest and trough have the same amplitude (for example, 4 cm and -4 cm), they will completely cancel each other out, resulting in an amplitude of 0 cm (because ).