What is

Light?

Light is Energy you can see.

The sun as all stars, is a source of Natural Light

The moon is not a source of light. It is merely the sun’s light

reflecting off its surface.

Light spreads out or radiates, so is called RADIANT ENERGY

Light producing Technologies are known as Artificial Light

Sources

Using Chemical Energy To produce light

Using Electrical EnergyTo produce light

LASER Technology

Incandescent Light

Incandescent light uses electricity to run through a tungsten filament which causes it to glow.

Disadvantage – only 5% of the electricity is used to generate light. 95% is lost to heat.

Advantage – cheap because it is a very OLD technology.

Fluorescent Light

• More expensive but lasts longer.

• More energy is devoted to generating light and less to heat.

• Toxic when chemicals released to air.

• Works by a gas being excited by electricity, causing it to emit UV light.

• The UV light causes the phosphorus lining to glow.

Phosphorescence

• Items coated in phosphor which absorb UV light.

• When the light source is removed, it glows in the dark.

• Disadvantage – slow to emit light and does not emit enough to light a room.

• Used to illuminate gauges in dark places.

• Also responsible for black lights causing us to glow in the dark.

• White really absorbs UV light which is why our white t-shirts and teeth glow

so much under a black light.

Chemiluminescence

• Light caused by a chemical reaction.

• Example: glow stick, you have to snap them to cause the chemicals to mix, and they then emit light.

Bioluminescence

• Living things that emit light.

• Some will argue that it’s a chemical reaction, which it is, but the chemicals are produced by living things.

LED Lighting• http://www.ehow.com/video_4872611_definition-led_.html

• Light Emitting Diode (LED) are used to light up many modern technologies. They are replacing incandescent bulbs because the LED lights last longer and use less electricity

Light on the sun is produced through Nuclear Fusion

First Basic Property of Light

LIGHT IS A FORM OF ENERGY