Young's double - slit experiment for interference is performed with two slits `3xx 10^(-3)` m apart and light of wavelength `6,600 overset @A`. If the screen is 1 m away from the slits,find out the position of the fourth dark fringe.

Explanation

`d = 3 xx 10^(-3) m`
`lambda = 6600 A = 6600 xx 10^(-10) m`
D = 1m
Position of dark fringe is given by
`y_(m) = (m + 1/2) (lambdaD)/2`
For fourth dark fringe, `m =4`
`y_(4) = (4+1/2) (6600 xx 10^(-10) xx 1)/(3 xx 10^(-3))`
`= 99 xx 10^(-5) m`
`y_(4) = 9.9 xx 10^(-4) m`