SOURCES OF LIGHT

luminous object: something that produces its own light The Moon is bright only because it reflects the Sun's light. Therefore, the Moon is NOT luminous.

The source of the sun's heat The sun 1. Incandescence: light that is emitted from a very hot object

Classic light bulbs are incandescent.

sodium vapour lamps a) electric discharge neon lights 2. Luminescence: light that is generated without heating the object - types:

LEDs (light-emitting diodes) Are another example of the source of light being electric discharge‏

b) chemiluminescence: light that is produced by a chemical reaction without a rise in temperature

c) bioluminescence: light that is produced by a biochemical reaction in a living organism

and mercury d) fluorescence: light that is emitted during exposure of the source to ultraviolet (UV) light compact fluorescent light (CFL) bulb tubular fluorescent light bulb

Efficiency of Fluorescent Vs. Incandescent Bulbs

Even though fluorescent bulbs are 4X as efficient as incandescent bulbs (20% vs. 5%), some people don’t like them because:  they find the light from fluorescent bulbs to be harsh.  these lamps contain small amounts of mercury vapour, a toxic metal.

Because they contain mercury, used fluorescent lamps CANNOT be thrown in the garbage. In Oakville, Rona & The Home Depot will take back your used fluorescent bulbs.

Uses of Fluorescence forensic science black light theatre fluorescent fish money

e) phosphorescence: light that is emitted due to exposure of the source to UV light, and that continues to be emitted for some time in the absence of the UV light