2009

Angle of incidence affects intensity.
Attenuation
In the real world, light diminishes over distance. Objects far from the light
source appear darker; objects near the source appear brighter. This effect is
known as attenuation.
In nature, light attenuates at an inverse square rate. That is, its intensity
diminishes in proportion to the square of the distance from the light source.
It is common for attenuation to be even greater when light is dispersed by
the atmosphere, especially when there are dust particles in the atmosphere,
or fog or clouds.
4980 | Chapter 18 Lights and Cameras