Optics Question 466

Question: In the ideal double-slit experiment, when a glass plate (refractive index 1.5) of thickness t is introduced in the path of one of the interfering beams (wavelength λ ), the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass plate is

Options:

A) 2λ

B) 2λ/3

C) λ/3

D) λ

Show Answer

Answer:

Correct Answer: A

Solution:

[a] Path difference due to slab should be integral multiple of λ . Hence, Δx=nλ Or (μ1)t=nλ,

n=1,2, Or t=nλμ1 For minimum value of t, n=1.

t=nλμ1=λ1.51=2λ



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