1. What is Light, baby don’t hurt me …
Production of light
What is Light, baby don’t hurt me …

2. Learning goals
We are learning the different ways light is produced.

3. Geometric optics terms
NON-LUMINOUS – objects that do not produce light
We see them because light reflects off them to our eyes
Ex. moon
LUMINOUS – objects that produce/emit light

4. luminous NATURAL – produce light without human intervention
Sun, lava, northern lights, lightning, firefly

5. luminous Artificial – light produced and controlled by humans
Car lights, neon signs, flashlights

6. Production of light Converted energy
Recall: Law of Conservation of Energy
Energy cannot be created or destroyed. It can only change/convert from one form to another
Example:
Input Energy Form
Converter
Output Energy Form
Chemical
Light, Heat

7. Methods of production

8. Incandescence Light from a heated object Various methods of heating
Adding thermal energy
Friction
Electricity
Chemical energy

9. Electric discharge
Electrons get excited and move to higher energy state due to collisions
As electrons move back to smaller orbit, energy is released
Natural
Lightning, static, northern lights
Artificial
Current passed through noble gas

10. fluorescence Emission of light when exposed to ultraviolet (UV) light
Phosphors – material that is excited by UV light emit white light
How it works:
Electric current through gas
Mercury emits UV
UV hits phosphor coating

11. phosphorescence
Some phosphors absorb UV or visible light, store the energy and emit it later as visible light
Glow in the dark stickers

12. chemiluminescence Result of chemical reaction
Little/no heat produced – cold light
Ex. Glow sticks

13. bioluminescence Chemiluminescence in living organisms
Ex. Glow worms, fire flies

14. triboluminescence Light produced by friction specifically in crystals
through the breaking of chemical bonds in the material.
Lifesavers in the dark – does it make a spark!?
Peeling two pieces of duct tape apart

15. Light emitting diode (LED)
electroluminescence
a material emits light after passing an electric current through it.
Christmas lights – doesn’t emit heat, doesn’t require a filament, more energy efficient.

16. “laser”
Laser Video
Light Amplified by Stimulated Emission of Radiation
Electromagnetic waves emitted exactly the same (direction and energy)
Pure in colour, very intense and concentrated into one narrow beam.

17. Learning goals
We are learning the different ways light is produced.