Film behind a double slit is exposed to light in the following way: First one slit is opened and light is allowed to go through that slit for time Δt. Then it is closed and the other slit is opened and light is allowed to go through that slit for the same time Δt. When the film is developed the pattern will be
A) one single slit pattern.
B) two superimposed single slit patterns, their centers displaced from each other by the distance between the two slits.
C) one double slit pattern.
D) two double slit patterns, their centers displaced from each other by the distance between the two slits.
E) random darkening of the film. (no pattern at all)

Question

Quizplus · Accepted Answer

When light is allowed to pass through one slit at a time, each slit produces its own single-slit diffraction pattern. Since the exposures are sequential and not simultaneous, there is no interference between the light from the two slits. Therefore, the final pattern on the film will be the superposition of two single-slit patterns, with their centers displaced by the distance between the slits.

Film Behind a Double Slit Is Exposed to Light in the Following