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Asked in GUJCET 2008 · Brewster's law and polarisation by reflection
Given: light reflected from a glass slab is completely polarised, and the angle of refraction then is 33.6°.
Idea: complete polarisation on reflection happens at the Brewster angle, and there the reflected ray and the refracted ray are at right angles to each other.
Putting the three rays along one normal, i_B + 90° + r = 180°, so i_B + r = 90°.
i_B = 90° - 33.6° = 56.4°.
Check with Brewster's law μ = tan i_B: tan 56.4° = 1.50, the refractive index of glass, as it should be.
The angle of incidence is 56.4°.
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