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Question: Answered & Verified by Expert
A single slit of width b is illuminated by a coherent monochromatic light of wavelength λ. If the second and fourth minima in the diffraction pattern at a distance 1 cm from the slit are at 3 cm and 6 cm respectively from the central maximum, what is the width of the central maximum? (i.e. distance between first minimum on either side of the central maximum)
PhysicsWave OpticsNEET
Options:
  • A 4.5 cm
  • B 1.5 cm
  • C 6.0 cm
  • D 3.0 cm
Solution:
1281 Upvotes Verified Answer
The correct answer is: 3.0 cm
For secondary minima dsinθ=nλ

sinθ=nλd

For second minima
n=2

sinθ=2λd=tanθ1=x1D


For fourth minima n=4

sinθ2=4λd=x2D

x2-x1=4λd-2λd=2λd= 6 -3 =  3cm

Width of central max=2λd=3 cm

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