1. What is Light?

2. Light is Energy you can see.

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

4. The moon is not a source of light
The moon is not a source of light. It is merely the sun’s light reflecting off its surface.

5. Light spreads out or radiates, so is called RADIANT ENERGY

6. Light producing Technologies are known as Artificial Light Sources
Using Chemical Energy
To produce light
LASER Technology
Using Electrical Energy
To produce light

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. LED Lighting
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

14. Light on the sun is produced through Nuclear Fusion

15. First Basic Property of Light
LIGHT IS A FORM OF ENERGY