Coherent visible light of a single frequency is incident normally on a double slit. This produces a pattern of bright and dark interference fringes on a screen, as illustrated below.
There are seven bright fringes.
Explain how the pattern of bright and dark interference fringes is formed.
The distance between the centres of bright fringe X and bright fringe Y in the pattern is 
. The slit spacing is 
. The distance from the slits to the screen is 
. Calculate the wavelength of the light incident on the slits.
The light is replaced by different visible light with a shorter wavelength. State how the new fringe separation will compare to the original fringe separation.
), they interfere constructively, producing bright fringes on the screen.
phase difference), they interfere destructively, producing dark fringes on the screen.
.
will decrease.
