1. 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

2. 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.

3. 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

4. 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