optical density

Optical density is a measure of how much a material resists and slows the transmission of light.

  • The optical density of a material is not directly related to its physical density.
  • The higher the optical density of a material, the slower light travels through it.
  • The lower the optical density of a material, the faster light travels through it.
  • A vacuum is not a medium and has zero optical density.
  • Light travels through a vacuum at the maximum possible speed of light which is 299,792 kilometres per second.
  • Optical density and refractive index are related properties.
    • In general, materials with higher optical density tend to have higher refractive indices and vice versa.
    • The greater the difference in refractive index between two materials, the more they will bend light when they come into contact.