Okay, so at θcrit is the light ray totally internally reflected, or is it not considered total internal reflection at this specific point (not until the angle is greater than θcrit) because the light ray is refracted tangent to the mediums and not "technically" reflected?

Thanks!

Okay, so at θcrit is the light ray totally internally reflected, or is it not considered total internal reflection at this specific point (not until the angle is greater than θcrit) because the light ray is refracted tangent to the mediums and not "technically" reflected?

Thanks!

The latter conclusion you reached is the correct one. Total internal reflection occurs when the angle of incidence is greater than the critical angle. When you're at the critical angle, you don't get total reflection, b/c refraction does occur (albeit at 90 degrees, but the light does refract).

Thanks, that's a very interesting point I never knew that caused me to lose a PS point on a practice exam :o I'll never forget it now! :D