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MHT CET202520 Apr 2025Morning ShiftPhysicsWave OpticsActual

In Young's double slit experiment, when light of wavelength 600 nm is used, 18 fringes are observed on the screen. If the wavelength of light is changed to 400 nm , the number of fringes observed on the screen is

Options

  1. A27
  2. B18
  3. C22
  4. D24

Correct answer

A. 27

Step-by-step solution

The fringe width in Young's double-slit experiment is determined by = D d , where is the wavelength, D is the slit-to-screen distance, and d is the slit separation. The number of fringes N visible within a fixed screen width W is N = W = Wd D . Since W , d , and D remain constant, N 1 , or equivalently N₁ ₁ = N₂ ₂ . Given ₁ = 600 , nm with N₁ = 18 fringes, and ₂ = 400 , nm , solve for N₂ : N₂ = N₁ ₁ ₂ = 18 600 400 = 27 . Final answer: 27

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