Question

A red Helium – neon laser with a wavelength of 632.8 nm illuminates two narrow horizontal slits with

gap distance 0.200 mm A pattern of interference bands then appears on a screen 1.00 m

from the slits

a) How far from the central maximum, in both radians and millimetres on the screen, is first

minimum?

        b) How far in millimetres on the screen, is the fifth maximum from the central maximum?

c) How big is the intensity in the fifth maximum compared to the intensity in the central maximum if

the gap width is half the gap distance?

Answer 1

a)

The angular position of first minimum

  

b)

c) Generally in intereference the intensity at all the maximas is equal.