8

Properties of Light 1131
incidence increases, the intensity of illumination
decreases.
Angle of incidence affects intensity.
Attenuation
In the real world, lig ht 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
thesquareofthedistancefromthelightsource.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.
A. Inverse decay
B.Inversesquaredecay
The graphs show the decay curves.
R efl ected Li ght a nd Ambient Light
The light an object reflects can i l luminate other
objects.Themorelightasurfacereflects,themore
light it contributes to illuminating other objects
in its environment.
Reflected light creates
ambient lig ht .Ambientlight
has a uniform intensity and is uniformly diffuse.
It has no discernible source and no discernible
direction.