Total Internal Reflection Can occur when light inside a glass block hits the edge at certain angles Remember – if light hits the boundary between two media it will pass straight through As you increase the angle of incidence, the ray gets bent However – at a particular angle called the Critical Angle, something strange happens

N REFRACTED RAY The ray is refracted parallel to the edge of the block at the Critical angle TOTAL INTERNAL REFLECTION OF LIGHT INCIDENT RAY

As we increase the angle of incidence As the angle of incidence increases, the ray is now only reflected back inside the block The edge of the block acts like a mirror The ray does not pass out of the block This is total internal reflection

But…. Total Internal Reflection only happens when……… The ray is travelling through a medium of higher refractive index and meets a boundary with a medium of lower refractive index (ie the light is slow moving and meets a medium where it would be fast moving)

So the 600 angle has total internal reflection

Internal Reflection This occurs only when light travels from more dense to less dense media.

Notice that light is not able to get out of the water at an angles greater than 42°