Question

The figure shows a Young's double slit experiental setup. It is observed that when a thin transparent sheet of thickness $t$ and refractive index $\mu$ 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 $\lambda$, $t$ will be

• A. None of the above
• B. $\frac{nD\lambda }{a(\mu -1)}$
• C. $\frac{D\lambda }{a(\mu -1)}$
• D. $\frac{2nD\lambda }{a(\mu -1)}$
• E. $\frac{2D\lambda }{a(\mu -1)}$

Answer 1

The correct option is A None of the above


Shift in the central maxima due to presence of slab is given as
$\text{shift}=\frac{D(\mu -1)t}{a}$
According to question
$\text{Shift}=n\times$fringe width

$\therefore \frac{D(\mu -1)t}{a}=\frac{n\lambda D}{a}$

$\Rightarrow t=\frac{n\lambda }{(\mu -1)}$