Critical angle and total internal reflection \

Cards (7)

    • 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
  • Critical Angle
    • 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)
  • Total Internal Reflection
    • 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 critical angle
  • 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 critical angle (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 cool air into warmer air
    • Cold air is denser than warmer air and has therefore a greater refractive index, which bends the light further away from the normal