Question

Laser light of wavelength 630 nm is incident on a pair of slits which are separated by 1.8 mm. If the screen is kept 80 cm away from the two slits, calculate:

1) fringe separation i.e. fringe width.

2) distance of 10^th bright fringe from the centre of the interference pattern

Answer 1

`lambda  = 630 nm`

`d = 1.8 xx 10^(-3)`

D = 0.80 m

1) `beta = (lambdaD)/d = (630 xx 10^(-9)xx 0.8)/(1.8 xx 10^(-3) ) = 2.8 xx 10^(-4) m`

2) `x = (nlambdaD)/d  = 10 xx 2.8 xx 10^(-4) = 2.8 xx 10^(-3) m`