In a Young.s double slit experiment wave length of light used is 5000 A and distance between the slits is 2mm, distance from slits is 1m. Find fringe width and also calculate the distance of `7^(th)` dark fringe from central birght fringe.

Explanation

`beta = (Dlamda )/( d ) = (1 xx 5 xx 10 ^(-7))/( 2 xx 10 ^(-3))`
` beta = 2. 5 xx 10 ^(-4) m`
`x _(n) = { n + (1)/(2)} (D lamda )/( d)`
` x _(gamma ) = (6.5 D lamda )/(d ) = ( 6.5 xx 1 xx 5 xx 10 ^(-7))/(2 xx 10 ^(-3))`
`x _(7) =1. 625 xx 10 ^(-3) m = 1.625 mm`