Question

A laser produces a beam of monochromatic light of wavelength 633 nm, which is incident
normally on a diffraction grating whose slits are vertical.
(i) Describe the form of the diffraction pattern that is seen on a distant screen. Comment
on the colour of the pattern also.
(ii) If the fifth order in the pattern is seen to occur at an angle of 39.3◦ with respect to the
incident beam, how many lines per mm does the grating contain

Answer 1