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Production of Light. 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. 1. Light from Incandescence.

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production of light1
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

1 light from incandescence
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

2 light from electric discharge
2. Light from Electric Discharge

Electric Discharge – the process of producing light by passing an electric current through a gas.

Ex #1: Lightning

Electricity passing through air (mixture of gases)

Ex #2: Neon signs

Electricity passing through different gases & producing different colours.

3 light from phosphorescence
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

4 light from fluorescence
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.
4 light from fluorescence1
4. Light from Fluorescence

Ex #2: Fluorescent light

Electric current applied  mercury atoms emit UV light  UV light strikes fluorescent coating  Visible light given off

5 light from chemiluminescence
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 stick

Breaking the glass chamber in the stick  mixing of chemicals in the stick  light produced

6 light from bioluminescence
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.

7 light from triboluminescence
7. Light from Triboluminescence

The production of light when certain crystals are scratched, crushed or rubbed.

Example: striking 2 sugar cubes against each other.

8 light from a led
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

11 3 laser
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.
laser
LASER
  • Very intense (as waves travel in same direction and are in unison)
laser1
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)