Question

In the Young's double slit experiment ,two slits $0.125mm$ apart are illuminated by light of wavelength $4500A^o$. The screen is $1m$ away from the plane of the slits. Find the separation between second bright fringes on both sides of central maxima.

Answer 1

Given : $D=1m$ $\lambda =4500\times {10}^{-10}m$ $d=0.125\times {10}^{-3}m$

Position of second bright fringe $y=\frac{2\lambda D}{d}$

$⟹y=\frac{2\times 4500\times {10}^{-10}\times 1}{0.125\times {10}^{-3}}=7.2\times {10}^{-3}m=7.2mm$

Separation between second bright fringe fringes on both sides $l=2y=2\times 7.2=14.4mm$