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Light is incident on a glass surface at an angle of incidence of 60 deg, and the reflected ray is found to be completely plane polarised. What is the refractive index of the glass?

1. 1.5
2. sqrt(3)
3. sqrt(2)
4. 3/2

Correct answer: sqrt(3)

Solution

When the reflected beam is fully plane polarised, the incidence angle equals Brewster's angle. By Brewster's law n = tan(theta_B) = tan(60 deg) = sqrt(3).

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