Question

Plane-polarized light of wavelength 0.59 μm falls on a trihedral quartz prism P (Fig. 5.34) with refracting angle θ = 30°. Inside the prism light propagates along the optical axis whose direction is shown by hatching. Behind the Polaroid Pol an interference pattern of bright and dark fringes of width Δx = 15.0 mm is observed. Find the specific rotation constant of quartz and the distribution of intensity of light behind the Polaroid.

Answer 1

Plane polarized light on entering the wedge decomposes into right and left circularly polarized light which travel with different speeds in P and the emergent light gets its plane of polarization rotated by an angle which depends on the distance travelled. Given that Δx = fringe width

Δx tan θ = difference in the path length traversed by two rays which form successive bright or dark fringes.

Let x = distance on the polaroid Pol as measured from a maximum. Then a ray that falls at this distance traverses an extra distance equal to