sources light. 1) natural sources of light sun! most important natural source of light
TRANSCRIPT
SOURCES LIGHT
1) Natural Sources of Light
SUN!
•most important natural source of light
Other Stars
Lightning
Fires
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
angler fish
• long spine with a bulb• used as a lure to attract prey
Jellyfish• use light to attract fish into their
tentacles
Flashlight fish
• use light to help to keep in a school
Fireflies
• use to attract mates
2) Artificial Sources of Light
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
Electric Discharge
• Production of light by passing an electric current through a gas
• E.g. halogen gases used often (e.g. neon)
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
• 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
Compact Fluorescent Bulbs• even though compact fluorescent
lights are more efficient than incandescent light bulbs, still 80% of energy is converted into heat
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
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
How Glow Sticks Work
Triboluminescence
• Production of light from friction• rubbing crystals together• quartz used in rattles by Aboriginal
people for flash lights
• 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.