Two optically flat plates of glass are kept at a small

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Two optically flat plates of glass are kept at a small angle θ as shown in the figure. Monochromatic light is incident vertically.

If the wavelength of light used to get a fringe spacing of 1 mm is 450 mm, the wavelength of light (in mm) to get a fringe spacing of 1.5 mm is __________

1. 675
2. 775
3. 575
4. 684

Correct Option: A

1 mm = 450 mm spacing = 1.5 mm

n =	2
	λ

1.5 = n ×	λ₂
	2

λ₂ = 1.5 × 450
λ₂ = 675 mm