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When light travels from an optically denser to a rarer medium, it bends away from the normal and at a specific angle of incidence, the angle of refraction is ${90}^{\circ}$. When the angle of incidence is equal to the Critical angle, the refracted ray grazes the path of separation of the two media. So at this angle, the speed of light would be that of the denser medium or that of the rarer medium?

Qmechanic
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Rishith Raj Raizada
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1 Answers1

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Based on this answer, the transmission coefficients of Frenels equations are $0$ and thus no light is refracted. Therefore any light that exists traveling at the speed of the denser medium because all light got reflected.

However, if light is travelling on a boundary (more generally), the beam has an actual width so anything on the rarer medium will travel at the speed light travels on that medium and vice versa for the denser medium. No light can travel in the $0$ width boundary.

JohnA.
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