# Formula: Condition for Constructive Interference Path difference    Integer    Wavelength

## Path difference

Unit
The path difference of two waves, which travel to the observation point (e.g. to the point where a bright interference fringe can be seen). The path difference thus indicates by how many wavelengths a wave leads or lags another wave.

For constructive interference, the path difference takes the following values: $\Delta s ~=~ 0,~ \lambda,~ 2 \, \lambda,~ 3 \, \lambda, ~...$

## Integer

Unit
Integer multiple of the wavelength takes the following values in the case of constructive interference: $$m = 0, 1, 2, ...$$. This integer indicates the factor by how much one wave precedes the other.

## Wavelength

Unit
Wavelength of the two waves under consideration. So the wavelength of the light used.

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