INTERFERENCE AND PROPERTIES OF A RESULTANT WAVEKate MacDonald Physics 101 Section 201

First, some definitions.• Resultant wave: The wave obtained by adding the

component waves.• Interference of waves: The physical phenomenon of two

or more waves combining to produce a resultant wave.

• When two component waves travelling in the same direction meet, they can reinforce each other, completely cancel each other out, or end up somewhere in between. The resultant wave incorporates properties from both the component waves.

• When reinforcement occurs, this is called constructive interference.

• When cancellation occurs, this is called destructive interference.

Constructive interference• When the crest of one wave coincides with the crest of

another, the waves are in phase and reinforce one another.

Destructive interference• When the crest of one wave coincides with the trough of

the other, the waves completely cancel each other out.

Resultant vs. Component: What is the same?

• When waves interfere, the resultant wave will have the same wavelength, frequency, speed, and direction as the component waves.

Resultant vs. Component: What is different?

• Phase constant and amplitude of the resultant wave will be different from the component waves, but depend explicitly on the values of those features in the component waves.

• Phase constant of a resultant wave is the mean phase constant of the component waves.

• Amplitude depends on the component amplitudes and difference between phase constants.

When you add waves with different wavelengths, the crests of the resultant wave will not all have the same amplitude.

Conclusion• Resultant waves are a sum of two or more separate

waves.• The phase, phase difference, amplitude, and wavelength

all factor into the resultant wave.• Waves may reinforce each other, cancel each other

completely, or fall somewhere in between.