In a young's double slit experiment, one of the slits is covered by a glass sheet of thickness `2.5xx10^(-5)`m. Due to this, the position of the central bright fringe is shifted to position originally occupied by the 30th bright fringe. If `lamda=5000` Å, then the refractive index of glass is

Options

A. 1.45
B. 1.5
C. 1.6
D. 1.65

Answer

C

Explanation

`X_(n)=30X=(30lamdaD)/(d) and X_(n)=(D)/(d)(n-1)t`
`therefore (30lamdaD)/(d)=(D)/(d)(n-1)t`
`(n-1)=(30lamda)/(t)=(30xx10^(-7)xx5)/(2.5xx10^(-5))`
`therefore (n-1)=0.6" "therefore n=1.6`