Double Slit Question?

A lamp emits light with wavelength of 580 nm. This light passes through two small slits which causes interference and creates an interference pattern on the the screen 1.5 m beyond the slits. If the spacing between the fringes of the interference pattern is 4.2mm, how far apart are the slits?

1 Answer
Feb 25, 2018

Fringe width(spacing between fringes) beta = lambda *D/d
where , lambda is wavelength of light , D is distance between slit and screen and d is distance between the slits

So , d = lambda*D/beta
= (580 * 10^-9 * 1.5 )/(4.2 * 10^-3 )m
=207.14 * 10^-6 m = 0.207 mm