Double Slit Question?

A lamp emits light with wavelength of 580 nm.580nm. This light passes through two small slits which causes interference and creates an interference pattern on the the screen 1.5 m1.5m beyond the slits. If the spacing between the fringes of the interference pattern is 4.2mm4.2mm, how far apart are the slits?

1 Answer
Feb 25, 2018

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

So , d = lambda*D/beta d=λDβ
= (580 * 10^-9 * 1.5 )/(4.2 * 10^-3 )m5801091.54.2103m
=207.14 * 10^-6 m 207.14106m = 0.207 mm0.207mm