When light travels from a denser medium to a less dense medium, the light will speed
Causing the light ray to bend away from the normal. Increasing the angle of incidence = an increase in the angle of refraction
CriticalAngle
Eventually, increasing the angle of incidence leads to the angle of refraction to become 90 degrees
The angle of refraction is equal to 90 degrees
The light is refracted along the surface between the two mediums (water and air)
TotalInternalReflection
Special case where the angle of refraction is bigger than 90 degrees
Means that the light rays are completely back into the first medium
Can only occur when the light is traveling from a slower medium into a faster one
Can only occur when the angle of incidence of a light ray is larger than the criticalangle
Angle of incidence is greater than critical angle
Increasing the angle of incidence so that it is greater the critical angle all light will be reflected within the medium, which is called total internal reflection
The angle of refraction is greater than 90 degrees
The light will be completely reflected back into the first medium
EG: retroreflector, mirages, triangular prisms
Fibre optics - light is used to transmit into a long glass and plastic cables
Diamonds
Sparkling of diamond is due to the cut of the diamond's faces & having a high index of reflection n=2.42). Diamonds have a very small criticalangle (24.4o) which will cause many of the incident rays to be reflected internally
Mirage
Optical illusion caused by atmospheric conditions, especially the appearance of a sheet of water in a desert or on a hot road caused by the refraction of light from the sky by heated air
Mirage can appear when light is traveling from coolair into warmerair
Cold air is denser than warmer air and has therefore a greater refractive index, which bends the light further away from the normal