1. The Production of Light
Shedding some light on the world…

2. How We See We see by light entering our eyes
This happens in 1 of 2 ways:
Luminous objects create their own light
Light bulb, Sun, TV
Non-Luminous objects only reflect light
Paper, planets, desks

3. How Light is Produced
Luminous Objects produce their own light in a variety of ways. For example:
Incandescence
Electric Discharge
Phosphorescence
Fluorescence
Chemiluminescence
Bioluminescence
Triboluminescence
Light-Emmiting Diode (LED)
LASER

4. Incandescence Producing light from a glowing hot object
Colours produced depend on the temperature
As temperatures increase, colours change from red, to yellow, to white, to a blueish-white.
Examples:
Stove, fire, incandescent light bulb

5. Electric Discharge
Producing light by passing electric current through a gas
Electrons are excited to higher orbits and then emit light when they fall back down
Different gasses produce different colours
Examples:
Lightening, neon lights

6. Phosphorescence
Producing light by absorbing UV light and emitting visible light over time
Phosphors store the energy until later
Examples:
Glow in the dark stickers, some watches

7. Fluorescence
Producing light by absorbing UV light and emitting visible light immediately
Examples:
Fluorescent lights, “black lights”, highlighters

8. Fluorescent Lights Makes use of electric discharge and fluorescence
Electric discharge in the tube causes mercury in the tube to emit UV light
Fluorescent materials on the outer wall of the tube then glow in the visible range
They don’t emit true white light, just a few distinct colours

9. Chemiluminescence
Production of light as the result of a chemical reaction
Little to no heat is produced
No electric current required
Examples:
Glow sticks

10. Bioluminescence Chemiluminescence occurring in a living organism
Developed for various reasons
Examples:
Firefly, Glow worm, Anglerfish

11. Triboluminescence Production of light from friction
Certain crystals produce light when crushed, rubbed or scratched
No known practical applications
Examples:
Eating wintergreens hard candy

12. Light-Emitting Diode (LED)
Producing light by passing electricity through a semi-conductor
Semi-conductor: A material allowing electricity to pass in one direction only
Low heat produced and very energy efficient
Examples:
Glowing light on electronics, Christmas lights, traffic lights

13. LASER Light Amplification by Stimulated Emission of Radiation
Produced using either special gasses or crystals
Laser light is all one colour (wavelength) traveling in a very narrow, focused beam
High and low energy lasers are available