Wave Optics

How is the direction of a ray related to a
wavefront ?

Which type of wavefront corresponds to a
parallel beam of tight ?

Is it necessary that the amplitude be constant
over a given wavefront ?

What is the main condition to produce
interference of light ?

Unpolarised light of intensity I0 is passed
through a polaroid. What is the intensity of the
light coming out of the polaroid ?

If width of slit is doubled, how will the intensity
of light be affected ?