JEE Main 2018 — Wave Optics Question with Solution
From: JEE Main 2018 (Offline)
Question
The angular width of the central maximum in a single slit diffraction pattern is 60°. The width of the slit is
1 m. The slit is illuminated by monochromatic plane waves. If another slit of same width is made near it,
Young’s fringes can be observed on a screen placed at a distance 50 cm from the slits. If the observed
fringe width is 1 cm, what is slit separation distance?
(i.e. distance between the centres of each slit.)
Choose an option
Show full solutionCorrect option: B
Correct answer
B25 m
Step-by-step explanation
Given 2 = 60o
= 30o
We know,
sin = n
for first minima n = 1,
At first minima
sin =
106 sin 30o =
= m
Now after making a new slit,
Fringe width, =
given, D = 50 cm and = 1 cm.
1 102 =
d = 25 106 m = 25 m.
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