Optics Question 228
Question: A parallel beam of monochromatic light of wavelength $ 5000{AA} $ is incident normally on a single narrow slit of width 0.001 mm. The light is focused by a convex lens on a screen placed on the focal plane. The first minimum will be formed for the angle of diffraction equal to
[CBSE PMT 1993]
Options:
A) $ 0{}^\circ $
B) $ 15{}^\circ $
C) $ 30{}^\circ $
D) $ 60{}^\circ $
Show Answer
Answer:
Correct Answer: C
Solution:
For the first minima $ d\sin \theta =\lambda $
$ \Rightarrow $ $ \sin \theta =\frac{\lambda }{d}\Rightarrow $
$ \theta ={{\sin }^{-1}}( \frac{5000\times {{10}^{-10}}}{0.001\times {{10}^{-3}}} )=30^{o} $
