In a Young's experiment, one of the slits is covered with a transparent sheet of thickness `3.6xx10^(-3)cm` due to which position of central fringe shifts to a position originally occupied by 30th fringe. If `lambda=6000 Å`, then find the refractive index of the sheet.

Explanation

The position of 30th bright fringe,
`y_(30) = (30 lambdaD)/(d)` Now position shift of central fringe is
`y_(0) = (30 lambda D)/(d)` , But we know,
`y_(0) = (D)/(d)(mu - 1) t`
`(30 lambda D)/(d) = (D)/(d) (mu -1) t`
`rArr (mu - 1) = (30 lambda)/(t) = (30xx (6000 xx 10^(-10)))/((3.6 xx 10^(-5))) = 0 . 5 `
` :. mu = 1 . 5 `