10.1 Light Energy and Its Sources

Text pages 289-293

(Visible) Light

• A form of energy that can be detected by the human eye

What is luminescence?Luminous simply means giving off light; most things in our world produce light

because they have energy that originally came from the Sun, which is the biggest,

most luminous thing we can see

Incandescence-make light by making

heat (very hot to touch!!)

Luminescent things, by contrast, make light when their atoms

become excited in a process that needs little or no heat to make it

happen.

Fluorescence: the emission of light by a substance that has absorbed light (or other electromagnetic radiation of a different

wavelength)= lower in temperature= Fluorescent materials produce light instantly= need to have electricity passed through them to keep them glowing

is a specific type of luminescence related to fluorescence. Unlike fluorescence, phosphorescence is a process in which energy absorbed by a substance is released relatively slowly (there is a delay). The object “glows” for a much longer period of time than in fluorescence

Electric discharge: electricity passing through a gas

Chemiluminescence: is the emission of light with very little heat as the result of a chemical reaction

Bioluminescence is chemiluminescence in living

organisms