Monichromatic lightof wavelenght 600 nm is used ina Young's double slilt experient. One of the slits is covered by a transparent sheet of thicknes `1.8xx10^-5` m made of a material of refractive index 1.6. How many fringe will shift due to the introduction of the sheet?

Explanation

When the light travels through as sheet of thickness t, the optical path travelled is `mut`, where `mu` is the refrctive index. When one of the slits is covered by the shet, air is replaced by the sheet and henc, the optical pasthchange by `(mu-1)t`. One fringe shifts when the optical path changes by one wavelength. Thus, the number of fringes shifted due to the introduction of the sheet is
`((mu-1)t)lamda=((1.6-1)xx1.8xx10^-5m)/(600xx10^-9m)=18`.