Optics Question 873

Question: A double slit, S1S2 is illuminated by a light source S emitting light of wavelength λ . The slits are separated by a distance d. A plane mirror is placed at a distance D in front of the slits and a screen is placed at a distance 2D behind the slits. The screen receives light reflected only by the plane mirror. The fringe-width of the interference pattern on the screen is

Options:

A) Dλd

B) 2Dλd

C) 3Dλd

D) 4Dλd

Show Answer

Answer:

Correct Answer: D

Solution:

[d] Due to reflection virtual source will be formed at distance D from mirror.

The effective distance of the screen =2D+2D=4D

Fringe width =4Dλd



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