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At what angle is light inside crown glass completely polarized when reflected from water, as in a fish tank?
Question by OpenStax is licensed under CC BY 4.0.
$41.2^\circ$
Solution Video

OpenStax College Physics for AP® Courses Solution, Chapter 27, Problem 94 (Problems & Exercises) (1:07)

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Video Transcript
This is College Physics Answers with Shaun Dychko. Light is traveling initially in some crown glass— that's the glass that this fish tank is made out of— and it reflects off this interface with the water that's inside the tank and when it reflects off, it's meant to be polarized if the angle of incidence is this Brewsters Angle. We need to know the indices of refraction of these materials so the crown glass we look up in table [25.1] and it has an index of refraction of 1.52 and the index of refraction of water is 1.33. So the tangent of Brewsters Angle is the second medium that the light is being reflected off of divided by the first medium that it's traveling in. So we take the inverse tan of both sides to solve for this angle and Brewsters Angle then is the inverse tan of n 2 over n 1. So that's the inverse tan of 1.33 divided by 1.52, which is 41.2 degrees.