What is the angle of refraction when the angle of incidence is equal to the critical angle?

Answer 1

Quick Answer:

The angle of incidence is not equal to the angle of refraction.

The angle of incidence is equal to the angle of reflection.

Better Answer:

(This answer applies to all waves, e.g. sound, ripples, earthquakes, but the answer is given in terms of light waves.)

The angle of incidence never equals the angle of refraction except in the peculiar circumstance when there is an interface between two materials of exactly the same index of refraction.

The angle of refraction is the direction of the wave exiting the surface and the angle of incidence is the angle entering the surface.

These two angles are related by Snell's law and by Snell's law one would conclude that the index of the medium of the incident beam would be exactly the same as the index of the transmitted beam. In optical terms, it would mean the wave propagates as though there were no interface and the two mediums were actually the same medium. In that case, there would be no reflection as well.

So, one does not expect this to happen, not because it can't, but because the wave travels through the surface as though the surface did not exist and that is both unusual and uninteresting.

Answer 2

Snell's law says the angle of refraction is 90 degrees.

One usually also says there is no refraction.

There is total internal reflection.

It is easy to see how this develops by simply drawing the rays representing the incident and refracted wave as the angle of incidence increases towards the critical angle. The angle of refraction approaches 90 degrees.

Answer 3

The angles of incidence and reflection are the angles between the normal to the

reflector and the arriving/leaving light ray respectively. They're equal, which is a

big help in solving problems that involve reflection.

-- When the angle of incidence is zero, that means that the incident light hits the

mirror perpendicularly, and it leaves along the same path on which it arrived.

-- When the angle of incidence is 90 degrees, the angle of reflection is too. The light

arrives and leaves parallel to the mirror at the reflection point. I wouldn't call that

much of a reflection, because the light never changes direction, and it doesn't really

matter whether the mirror is even there or not.

Answer 4

Also zero, if the angle of incidence is zero, then the light beam (or other wave/beam) entering the medium is at 90 degrees to it's surface, so no refraction occurs.

Answer 5

Yes only if the refractive index is 1. This means both the medium are of the same optical nature

Otherwise they are not equal

Answer 6

It equals the angle of reflection.

Answer 7

If the angle of incidence increases and the indexes of refraction stay the same, what happens to the angle of refraction?