SunlightSunlight

Plasma at extremely high temperatures.

6,000 ºC Outer 1.5x107 ºC Inner

[http://www.astronomy.com/asy/objects/images/sun_full_disk_soho_09_14_1997.jpg]

Rather uniform spectrum of colors

[http://www.videoessentials.com/images/res_spectral12.gif]

Incandescent LightIncandescent Light These heat a

piece of metal until it produces light.

The thin piece of metal is called a filament.

[http://www.videoessentials.com/images/res_spectral12.gif]

Mainly red/orange/yellow in spectrum of incandescent lights

Incandescent LightIncandescent Light

About 80% of the energy used is converted to heat (infrared).

Fluorescent LightsFluorescent Lights

A glass tube is covered with phosphors that give off light when UV rays from the gas inside are given off.

[http://www.videoessentials.com/images/res_spectral12.gif]

Mainly blue/green in spectrum of fluorescent lights

Fluorescent LightsFluorescent Lights

Uses one-fifth the energy of an incandescent light bulb.

Can contain mercury so must be recycled after use.

Neon LightsNeon Lights

Electricity is passed through a glass tube filled with gas, and the particles collide and give off light.

This creates an emission spectrum of “lines” at certain colors

[http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/modpic/neoncomp.jpg]

LasersLasers

Atoms of a gas are charged with energy and they in turn all give off light with the same wavelength.

LasersLasers

Used in medicine and in reading optical data (CD’s, DVD’s)

Tungsten-Halogen LightsTungsten-Halogen Lights

The filament is made of the Tungsten which can create a tremendous amount of heat, and light.

[http://www.daviddarling.info/images/tungsten_halogen_lamp.jpg]

Has a rather uniform spectrum and is somewhat energy efficient.

[http://www.molecularexpressions.com/primer/lightandcolor/images/lightsourcesfigure3.jpg]

Sodium-Vapor LampsSodium-Vapor Lamps

Sodium metal becomes very hot and changes to a vapor to produce yellow-orange light.

[http://upload.wikimedia.org/wikipedia/en/6/63/Na-lamp-2.jpg]

Can be used outdoors to reduce light pollution at night.

[http://www.sao.arizona.edu/FLWO/LIGHT/MontePatria2.jpg]

Uses of LightUses of Light

Polarizing Filters Only light waves

that are vibrating in one direction pass through.

Used in sunglasses to block “glare”

Uses of LightUses of Light

Optical Fibers Light waves pass

through a glass tube for communication purposes.

Telephone, TV, Internet

Total Internal Reflection allows the light waves to “travel” through the tube.

Click here for a demonstration