SOURCES OF LIGHT

Sun- nuclear fusion

Process: H + H He + Energy All elements are made like this… we are all

star dust!

Qualities and Applications: All colours and types of light emitted This light energy fuels life on earth

Incandescence- light emitted from a very hot object

Process: Electrons passed through a wire

(electricity) generates heat.

Qualities and Applications: Very Bright Very inefficient only 5% of energy

converted to light 95% to heat

Electric Discharge-light emitted from a heated gas, instead of a heated wire.

Process: Electrons flowing through a gas, heat it up,

and light is emitted Common form is the sodium vapour bulb

where electricity is passed through a tube with a drop of sodium and mercury.

Fluorescence-substances that convert UV light into visible light

Process: Form of electric discharge, light emitted from

mercury in a tube. Mercury produces ultra violet light which hits phosphor coating on glass which emits visible light.

Qualities and Applications: 80% efficient 20% lost as heat Last 10x longer than incandescent bulbs Fluorescence dyes in money, semen, blood

Luminescence-light produced without heating an object

Process: The energy used to excite the atoms can come from a

variety of sources. For example, Fluorescence is a type of luminescence because the energy used to excite the phosphor in a fluorescent bulb comes from ultraviolet light.

Phosphorescence, chemiluminescence, and bioluminescence are types of luminescence.

Phosphorescence-light emitted from phosphorescent materials

Process: Materials store energy and release it

slowly over time

Qualities and Applications: Glow in the dark objects Dim lights

Chemiluminescence-light produced from the energy released in a chemical reactionQualities and Applications: Glow sticks Dim/long lasting lights

Bioluminescence-light produced by chemiluminescence inside a living organism

Qualities and Applications: Fire flies Some fish Jelly fish Bacteria Algae Most produced by bacteria inside other

living things