Intensity measures the amount of light energy passing through a unit area perpendicular to the direction of light propagation.

  • Intensity measures the energy carried by a light wave or stream of photons.
  • When light is modelled as a wave, intensity is proportional to the square of the amplitude.
  • When light is modelled as a particle, intensity is proportional to the number of photons present at any given point in time.
  • The intensity of light falls off as the inverse square of the distance from a point light source increases.
  • Light intensity at any given distance from a light source is directly related to the power of the light source and the distance from the source.
  • The power of a light source describes the rate at which energy is emitted and is measured in watts.
  • The intensity of light is measured in watts per square meter (W/m²) and is also commonly expressed in lux (lx).