Question

A double slit S₁— S₂ is illuminated by a coherent light of wavelength λ. The slits are separated by a distance d. A plane mirror is placed in front of the double slit at a distance D₁ from it and a screen ∑ is placed behind the double slit at a distance D₂ from it (figure 17-E2). The screen E receives only the light reflected by the mirror. Find the fringe-width of the interference pattern on the screen.

Answer 1

It can be seen from the figure that, the apparent distance of the screen from the slits is,