A young's double slit apporatus is immersed in a liquid of refractive index 1.33.It has slit separation of 1 mm and interference pattern is observed on the screen at a distance 1.33 m from plane of slits.The wavelength in air is `6300 Å`
One of the slits of the apparatus is covered by a thin glass sheet of refractive index 1.53. Find the smallest thickness of the sheet to interchange the position of minima and maxima .

Options

A. 2.57 mm
B. 1.57 mm
C. 3.27 mm
D. 4.18 mm

Answer

B

Explanation

`Deltax = (mu_2/mu_1-1)t=lambda/2`
`:. t=lambda/(2(mu_2/mu_1-1))`
`=((6300 xx 10^(-10)//1.33))/(2(1.53/1.33-1))`
`=1.575 xx 10^(-3) m`
=1.575 mm.