A transparent paper (refractive index = 1.45) of thickness 0.02 mm is pasted on one of the slits of a Young's double slit experiment which uses monochromatic light of wavelength 620 nm. How many fringes will cross through the centre if the paper is removed ?

Answer

A, D

Explanation

Given that `mu=1.45`
`t=0.02mm`
`=0.02xx10^-3m`
and `l=620 nm=620xx10^-9m`
We know when the transparent paper is pasted in one the slits, the optical path changes by `(mu-1)f`.
`again for shift of one fringe the opticasl path should be changed by l.
`So Number of fringes crossing throgh the centre is given by
`n=((mu-1))/lamda`
`=(0.45xx0.02xx10^-3)/(620xx10^-9)`
`=14.5`