Optics Question 883

Question: In a Young’s double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is :

Options:

A) 9.75 mm

B) 15.6 mm

C) 1.56 mm

D) 7.8 mm

Show Answer

Answer:

Correct Answer: D

Solution:

[d] For common maxima, n1λ1=n2λ2

n1n2=λ2λ1=520×109650×109=45 For λ1

y=n1λ1Dd , λ1=650nm

y=4×650×109×1.50.5×103 or y=7.8mn



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