5CH - Path difference

As we saw today, path difference is what causes interference. The path difference is the difference in distance travelled by the waves. This difference in distance will mean that the waves become either in phase or out of phase. Waves that arrive in phase will interfere constructively and waves that arrive out of phase will interfere destructively.

We introduced two equations for working with path difference, one for maxima and one for minima. You need to be able to select the correct one for the given situation. Remember of course that the path difference equation for a minima isn't actually very useful! It might be best to use p.d. = (n - 1/2)λ.

This will not be given in the data booklet though.