Wave Optics

JEE Main level, single correct, medium

98 of 191

Question 98 of 191

In a double slit experiment, when a thin film of thickness tt having refractive index μ\mu is introuduced in front of one of the slits, the maximum at the centre of the fringe pattern shifts by one fringe width. The value of tt is (λ(\lambda is the wavelength of the light used):

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Answer: (D) λ(μ−1)\dfrac{\lambda }{(\mu -1)}

Shift =(μ−1)tDd=\left(\mu -1\right)t\dfrac{D}{d}
Fringe width (β)=λDd(\beta )=\dfrac{\lambda D}{d}
(μ−1)tDd=λDd(\mu -1) t\dfrac{D}{d}=\lambda \dfrac{D}{d}
t=λμ−1t=\dfrac{\lambda }{\mu -1}

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