objects can either be: luminous (produce their own light) ex: sun non-luminous can be seen...
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PRODUCTION OF LIGHT
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Production of Light
Objects can either be: Luminous (produce their own light) ex:
Sun Non-luminous can be seen because it
is able to reflect light
Q: So what are the sources for luminous objects?
A: 8 different luminous sources
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1. Light from Incandescence
Incandescence – light produced due to high temperature.
Ex #1: Regular light bulbs (Thomas Edison)Electricity passes through tungsten wire becomes very hot and emitted light:~90% released as Infrared light (not visible to naked eye, but we feel the heat)~10% released as visible light
Ex #2: Metal heated up
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2. Light from Electric Discharge
Electric Discharge – the process of producing light by passing an electric current through a gas.
Ex #1: LightningElectricity passing through air (mixture of gases)
Ex #2: Neon signsElectricity passing through different gases & producing different colours.
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3. Light from Phosphorescence
Phosphorescence– the process of producing light by absorption of UV light by special materials (called phosphors) resulting in emission of visible light over a period of time
“Glow in the dark” items
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4. Light from Fluorescence
Fluorescence – the immediate emission of visible light as a result of absorption of UV light.
Ex #1: Fluorescent dye in detergent Clothes look brighter due to extra visible light given off.
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4. Light from Fluorescence
Ex #2: Fluorescent lightElectric current applied mercury atoms emit UV light UV light strikes fluorescent coating Visible light given off
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5. Light from Chemiluminescence
What does the name suggests?Chemiluminescence is the production of light as a result of chemical reaction, with little or no heat produced.
Example: Glow stickBreaking the glass chamber in the stick mixing of chemicals in the stick light produced
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6. Light from Bioluminescence
The production of light in living organisms as a result of chemical reaction, with little or no heat produced.
Example: Dinoflagellate is a marine plankton that will glow in presence of danger/predator.
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Bioluminescence
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7. Light from Triboluminescence
The production of light when certain crystals are scratched, crushed or rubbed.
Example: striking 2 sugar cubes against each other.
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8. Light from a LED
LED (Light-Emitting Diode): an electronic device that allows an electrical current to flow in only one direction.
Need special materials called semiconductors.
Differences from incandescent bulb: No filament required
Not much heat produced
More Energy efficient
Example: Christmas lights
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11.3 - LASER
LASER: Light Amplification by Stimulated Emission of Radiation
Produces electromagnetic waves of the same Energy level so no separation of colour when going through triangular prism. Very pure colour emitted.
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LASER
Very intense (as waves travel in same direction and are in unison)
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LASER
Laser’s unique properties makes it useful in measuring large distances, such as the distance from moon to earth.
Q: How do they do it?Apollo 11, 14 and 15 mission left corner-cube reflectors on the moon.
Distance calculated as 385,000 km (with an accuracy of 3 cm)