Wave Optics - Result Question 28

30. For a parallel beam of monochromatic light of wavelength ’ λ ‘, diffraction is produced by a single slit whose width ’ a ’ is of the wavelength of the light. If ’ D ’ is the distance of the screen from the slit, the width of the central maxima will be :[2015]

(a) Dλa

(b) Daλ

(c) 2Daλ

(d) 2Dλa

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Solution:

  1. (d) Linear width of central maxima Y

=D(2θ)=2Dθ=2Dλaθ=λa

The central maxima lies between the first minima on both sides.

The angular width ’ d ’ central maxima =2θ=2λb

Linear width of central maxima =2Dθ=2Dλb

b= width of slits and D= distance between slit and screen.



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