opticsLight and Applications of Optics

Producing Light(p.278)

• Luminous objects, such as our Sun, produce their own light

• Non-luminous objects, such as the Moon, do not produce their own light

• Most objects are non-luminous• There are many different ways light can be

produced from luminous sources

3min

Incandescence

1min

how it's made 5 min

•The production of light from high heat•E.g. an incandescent bulb (tungsten filament) or a candle•Only 5-10% efficient!!

Electric Discharge• The production of light by passing an electric current through a gas• Eg. a street lamp or neon sign

8min

4min

Phosphorescence"glow in the dark"

• The process of producing light by the absorption of UV radiation resulting in the emission of visible light over an extended period of time

• E.g. glow-in-the-dark toys

22 sec

Fluorescence

•The immediate emission of visible light as result of absorption of UV radiation

•Eg. Fluorescent bulbs (tube or compact)

•A fluorescent bulb uses both electric discharge and fluorescence

Fluorescence• The bulb is filled with mercury vapour and coated with a fluorescent material (phosphor)• The electricity causes the mercury atoms to emit UV radiation, which then strikes the fluorescent

coating which emits visible light

1.5 min

8min

Chemiluminescence• The production of light as a results of chemical reaction with little to no heat produced• Eg. Glowstick or luminol

3min

elephant toothpaste 1min

Bioluminescence• The production of light in living organisms as a result of a chemical

reaction with little or no heat produced• Eg. Fireflies, some types of bacteria, fungi, marine invertebrates, and fish

2min

13 sec

3min

•The production of light from friction as a result of scratching, crushing, or rubbing certain crystals•Eg. Rubbing two sugar cubes together or biting Wint-O-Green lifesavers

•http://www.youtube.com/watch?v=6Q9s13HHGsI

Triboluminescence

•Light-emitting diodes (LED) are electronic devices in which light is produced as a result of an electric current flowing through a semiconductor•Are extremely energy efficient•Eg. Christmas lights

LED’s

•Read pg. 470-476 in your textbook•Do Q# 2,4-6, 8-11 on pg. 476

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