I'm pretty sure internal reflection is the basic principle behind how fiber optic cables work. Light is sent as data and reflects internally with the same material where the covering of the cable has a low refractive index and keeps the light internal.
Actually, when TIR happens, light can still transmit through the boundary. Its amplitude just decays exponentially.
will we need to know the derivation of this for the exam? or only its result aka snell's law?