In Young's double slit experiment the fringes are formed at a distance of 1 m from double slit of separation 0.12 mm calculate.
(i). The distance of 3rd dark band from the centre of the screen.
(ii). The distance of 3rd bright band from the centre of the screen, Given `lambda=6000Å`

Explanation

(i). For `m^(th)` dard fringe `x_(m)=(2m-1)(Dlamda)/(2d)` given D=1m=100cm, d=0.12mm=0.012cm
`x_(3)=((2xx3-1)xx100xx6xx10^(-7))/(2xx0.012)=1.25cm[becausem=3` and `lamda=6xx10^(-7)m]`
(ii). For `n^(th)` bright fringe `x_(n)=(nDlamda)/(d)impliesx_(3)=(3xx100xx6xx10^(-7))/(2xx0.02)=1.5xx10^(-2)m=1.5cm[becausen=3]`