Correct option (a) plane polarized
Explanation:
When a circularly polarized beam passes through a quarter wave plate, it becomes plane polarized. Because the quarter wave plate is plate which can produces the path difference of λ/4 and phase difference of π/2 between ordinary and extra ordinary ray.
The total phase difference after QWP is δ = δ1 + δ2 = π/2 + π/2 = π
Thus output light will be linearly polarized
