As shown in the figure, a ray AB of unpolarized light enters from water of refractive index n(w) = 4/3 into a medium of refractive index n(p) = 4/√3 after passing through a glass plate of refractive index n(g) = 1.5 and a layer of water. At a particular incident angle i the reflected ray CD is polarized in the direction as shown in the figure. The value of i (in degrees) is:

Question

G1 Physics · Accepted Answer

At the final water-medium interface, the reflected light is completely polarized, so the incidence angle there is the Brewster angle. Using tan i(B) = n(p)/n(w) = [4/√3]/[4/3] = √3 gives i(B)=60°. Applying Snell's law through the parallel layers gives the required incident angle i = 60°.