Question:
In a Young's double slit experiment, 16 fringes are observed in a certain segment of the screen when light of a wavelength 700 nm is used. If the wavelength of light is changed to 400 nm, the number of fringes observed in the same segment of the screen would be
In a Young's double slit experiment, 16 fringes are observed in a certain segment of the screen when light of a wavelength 700 nm is used. If the wavelength of light is changed to 400 nm, the number of fringes observed in the same segment of the screen would be
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Fringe width is proportional to wavelength, so the number of fringes in a fixed segment is inversely proportional to wavelength.
Updated On: Nov 5, 2026
- 28
- 24
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- 18
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The Correct Option is A
Solution and Explanation
Fringe width \(\beta=\frac{\lambda D}{d}\). Number of fringes in a segment of length \(L\): \(N=\frac{L}{\beta}=\frac{Ld}{\lambda D}\propto\frac{1}{\lambda}\).
\(\frac{N_2}{N_1}=\frac{\lambda_1}{\lambda_2}=\frac{700}{400}\).
\(N_2=16\times\frac{700}{400}=28\).
Answer: (1) 28
\(\frac{N_2}{N_1}=\frac{\lambda_1}{\lambda_2}=\frac{700}{400}\).
\(N_2=16\times\frac{700}{400}=28\).
Answer: (1) 28
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