Wave Optics

JEE Main level, single correct, medium

100 of 191

Question 100 of 191

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\mu is put in front of one of the slits, the central maximum gets shifted by a distance equal to n fringe width. If the wavelength of light used is λ\lambda then tt will be:

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Answer: (B) nλ(μ−1)\dfrac{n\lambda }{(\mu -1)}

Shift in central maxima =Da(μ−1)t=\dfrac{D}{a}\left(\mu -1\right)t
Fringe width =Dλa=\dfrac{D\lambda }{a}
It's given,
Da(μ−1)t=nDλa\dfrac{D}{a}\left(\mu -1\right)t=n\dfrac{D\lambda }{a}
t=nλμ−1t=\dfrac{n\lambda }{\mu -1}

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