Optics Question 1094

Question: In double slit experiment, the angular width of the fringes is 0.20o for the sodium light (l = $ 5890{AA} $ ). In order to increase the angular width of the fringes by 10%, the necessary change in the wavelength is

[MP PMT 1997]

Options:

A) Increase of $ 589{AA} $

B) Decrease of $ 589{AA} $

C) Increase of $ 6479{AA} $

D) Zero

Show Answer

Answer:

Correct Answer: A

Solution:

$ \theta =\frac{\lambda }{d};\theta $ can be increased by increasing l, so here l has to be increased by 10% i.e., % Increase $ =\frac{10}{100}\times 5890=589{AA} $



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