Question

Two slits `0,125 mm` apart are illuminated by light of wavelength `4500 Å`. The screen is `1m` away, from the plane of the slits. Find the separation between the 2nd bright fringe on both sides of the central maximum.

Answer 1

`d = 0.125 mm. = 0.125 xx 10^(-3)m`,
`lambda = 4500 Å = 4500 xx 10^(-10)m = 4.5 xx 10^(-7)m`,
`D = 1 m, n = 2`
If `x` is distance of 2nd brigth fringe on each side, then separation between them
`= 2x = 2 n lambda(D)/(d) = (2 xx 2 xx 4.5 xx 10^(-7) xx 1)/(0.125 xx 10^(-3))m = 144 xx 10^(-4)m = 14.4 mm`