Question

There are two sets of apparatus of Young?s double slit experiment. In set A, the phase difference between the two waves emanating from the slits does not change with time, whereas in set B, the phase difference between the two waves from the slits changes
rapidly with time. What difference will be observed in the pattern obtained on the screen in the two set ups?

Answer 1

Dear student,
Set A: stable interference pattern, the positions of maxima and minima does not change with time. Set B : positions of maxima and minima will change rapidly with time and an average uniform intensity distribution will be observed on the screen

The necessary condition for sustainable interference pattern is that either the two sources should not have a phase difference so they should have a constant phase difference throughtout the experiment.
Regards