Monochromatic light with a wavelength of 5.0 E -7 meter passes through two narrow slits, producing an interference pattern on a screen 3.0 meters away. The first order bright band lines 2.0 E -2 meters away from the central bright maxima. What is the distance between the slits?

Answer 1

There are bright bands where
x = m (lambda)D/d

d is the slit separation (which is what you want to solve for).

x = distance from central bright band to first order maximum = 0.02 m
m = 1 for first order interference
D = distance to screen = 3.0 m
lambda = wavelength = 5*10^-7 m

Solve for d