Illumination
When an object receives a lot of light, it is brightly lit
or illuminated. Thus, we can define illumination as the amount of
light falling on a unit area of surface.
However, this concept cannot be applied to transparent and
transclucent objects as they allows light to pass through completely and the other type
disperse light respectively
Luminiscence
Incandescence refers to emitting light while utilising
heat. Luminiscence is directly the opposite. It is the emission of
light in the absence of heat.
This occurs when energy is absorbed by objects other than
heat and changing them to light energy. Luminiscent animals such as glowworms and
fireflies glow due the the change of the chemicals in the bodies to the form of light
energy.
A television screem has luminiscent materials that sparks
off and lights up when electrons strike them. Generally, there are 2 types of luminiscence
;
1) Inphophorescence
It refers to a substance which absorbs energy readily and
later giving it off as light. Certain plants work in this way , storing energy in the
daytime and then glow in the night.
2) Influorescence
In this case, light is emitted almost immediately. Bright
fluorescent paints take in light of various colours or invisible ultraviolet rays and
gives off light of 1 colour. This light is normally much brighter than normal reflected
light.
