Index of refraction

The refractive index of a medium is a measure of how much the speed of light is reduced when it passes through the medium compared to its speed in a vacuum.

  • The refractive index of a medium is a numerical value and is represented by the symbol n.
  • Because it is a ratio of the speed of light in a vacuum to the speed of light in a medium there is no unit for refractive index.
  • The refractive index of water is 1.333, meaning that light travels at 2/3 the speed in water compared to a vacuum.
  • If the refractive index of a medium is 1.5, for example, light travels at 2/3 the speed through glass compared to a vacuum.
  • As light undergoes refraction, its wavelength changes, but its frequency remains the same.
  • As light undergoes refraction its frequency remains the same.
  • The energy transported by light is not affected by refraction or the refractive index of a medium, but the intensity of the light can be affected.