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Question:

The figure shows a Young's double slit experimental setup. It is observed that when a thin transparent sheet of thickness t and refractive index μ is put in front of one of the slits, the central maximum gets shifted by a distance equal to n fringe widths. If the wavelength of light used is λ, t will be

2Dλ/a(μ-1)

nDλ/a(μ-1)

2nDλ/a(μ-1)

No answer

Dλ/a(μ-1)

Solution:

Correct option is E. No answer
path difference at central maxima Δx=(μ-1)t, whole pattern will shift by same amount which will be given by
(μ-1)tD/d = nλD/d
according to the question
t = nλ/(μ-1)
no option is matching