What is Light? Light is a form of energy that travels very fast If something travels at the speed of light, it could circle the earth 7.5 times in 1 second! Light travels in straight lines Light does not require a medium (other substance) for transmission; it is transferred through radiation Do you know another form of energy that does need a medium to transmit it? Heat

The Electromagnetic Spectrum Light is one of many different types of electromagnetic waves The human eye can only detect visible light The electromagnetic waves below decrease in size as you go from radio waves to gamma waves.

Method How Light is Produced Example incandescence An object is heated to a high temperature molten glass that glows electric discharge An electric current passes through a gas lightening phosphorescence A special material absorbs UV light and releases visible light over a period of time glow-in-the-dark stickers fluorescence A material absorbs UV light and immediately releases visible light fluorescent light chemiluminescence A chemical reaction produces light directly light stick bioluminescence An organism releases light through a chemical reaction in its body firefly triboluminescence Certain crystals are scratched, crushed, or rubbed biting a wintergreen candy

THE LASER – A SPECIAL TYPE OF LIGHT Light from a laser has special properties. A laser produces electromagnetic waves of exactly the same energy level This results in visible light being of a very pure colour A red laser light entering a triangular prism will still look red on exit Laser light is also very intense because the electromagnetic waves travel in the same direction and are exactly in unison Never look directly at a laser beam