Fringes are produced with monochromatic light of wavelengths `4.45xx10^(-5)` cm. A thin glass plate of R.I. 1.5 in then normally placedin one of the paths of interfering waves and the central bright band of the fringe system is found to move into the position, previously occupied by the thrie bright band from the system. The thickness of glass plate will be

Options

A. `32.7xx 10^(-4) cm`
B. `32.7xx 10^(-5) cm`
C. `16.7xx 10^(-5) cm`
D. `12.5xx 10^(-5) cm`

Answer

B

Explanation

` lambda =5.45 xx 10^(-5) cm, mu = 1.5 , Delta beta = 3 beta, t= ?`
` Delta beta =(beta)/(lambda)( mu-1)t`
` 3 beta =( beta)/(lambda) (mu-1)t`
`:.t=(3lambda)/(mu-1)=(3xx5.45xx10^(-5))/(1.5-1)`
`t=32.7xx10^(-5) cm`