Draw the intensity pattern for single slit diffraction and double slit interference. Hence, state two differences between interference and diffraction patterns.

OR

Unpolarised light is passed through a Polaroid P₁. When this polarised beam passes through another polaroid P₂ and if the pass axis of P₂ makes angle θ with the pass axis of P₁, then write the expression for the polarised beam passing through P₂. Draw a plot showing the variation of intensity when θ varies from 0 to 2𝜋.

The above figure shows the intensity pattern for single-slit diffraction and double slit interference. 

The two differences between interference and diffraction patterns: (1) Interference fringes are of the same width while diffraction fringes are not of the same width. 
(2) In interference pattern, all bright bands are of same intensity while in diffraction pattern, all bright bands are not of same intensity.

OR

When unpolarised light of intensity I_o is passed from P1, we get intensity of light = I₀/2. 
When this polarised light is passed from P2 having ∠θ with P1, we get, 
I = I₀2cos2θ 
Variation of intensity with θ: