1. SOURCES LIGHT

2. 1) Natural Sources of Light

3. SUN!
most important natural source of light

4. Other Stars

5. Lightning

6. Fires

7. Bioluminescence
the production of light as a result of a chemical reaction in a living thing
sea creatures use this in very deep water where no light is
use light to see prey/scare predators/camouflage

8. angler fish
long spine with a bulb
used as a lure to attract prey

9. Jellyfish
use light to attract fish into their tentacles

11. Flashlight fish
use light to help to keep in a school

13. Fireflies
use to attract mates

15. 2) Artificial Sources of Light

16. Incandescent Light Production of light as a result of high temperature
bulbs contain a filament or thin wire (tungsten) that is heated up by electricity and then glows
Only 5%-10% effective

17. Electric Discharge
Production of light by passing an electric current through a gas
E.g. halogen gases used often (e.g. neon)

18. Fluorescent Light
the immediate emission of visible light as a result of the absorption of UV light
E.g. detergents, highlighters, fluorescent lights
Demo: rocks + UV light

19. bulb filled with a gas such as mercury vapour
When mercury vapour is exposed to electricity it emits UV light
bulb is coated with a white powder called phosphor
phosphor glows if exposed to UV radiation

20. Compact Fluorescent Bulbs
even though compact fluorescent lights are more efficient than incandescent light bulbs, still 80% of energy is converted into heat

21. Phosphorescent Light
The process of producing light by the absorption of UV light resulting in the emission of visible light over an extended period of time
Different from fluorescent because phosphorescent materials glow in the dark for some time after being energized by light

22. Chemiluminescence
light produced from chemical reactions (little heat produced)
ex. luminol used in forensics: glows when it reacts to iron in blood
ex. glow sticks

23. How Glow Sticks Work

24. Triboluminescence Production of light from friction
rubbing crystals together
quartz used in rattles by Aboriginal people for flash lights

25. Complete Worksheet before end of class.
Do pg. 476 #1-4, 6,9,10
You should have this mostly done by the end of class.