Optics Question 1025

Question: Interference was observed in interference chamber when air was present, now the chamber is evacuated and if the same light is used, a careful observer will see

[CBSE PMT 1993; DPMT 2000; BHU 2002]

Options:

A) No interference

B) Interference with bright bands

C) Interference with dark bands

D) Interference in which width of the fringe will be slightly increased

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Answer:

Correct Answer: D

Solution:

The refractive index of air is slightly more than 1. When chamber is evacuated, refractive index decreases and hence the wavelength increases and fringe width also increases.