In double slit experiment , the distance between two slits is `0.6mm` and these are illuminated with light of wavelength `4800 Å`. The angular width of dark fringe on the screen at a distance 120 cm from slits will be

Options

A. `8xx10^(-4)` rad
B. `6xx10^(-4)` rad
C. `4xx10^(-4)` rad
D. `16xx10^(-4)` rad

Answer

A

Explanation

Given, `d=0.6mm=0.6xx10^(-3)m`
`lambda=4800"Å"=4.8xx10^(-7)m,n=1`
Angular fringe width of first minima
`(2x)/(D)=2(2n-1)(lambda)/(2d)=(2xx1-1)(lambda)/(d)`
`therefore (2x)/(D)=((2-1)xx4.8xx10^(-7))/(0.6xx10^(-3))=8xx10^(-4)` rad