Types of Light Emissions - PowerPoint Presentation

Types of Light Emissions
Types of Light Emissions

Types of Light Emissions - Description


Luminous an object that emitsproduces its own light eg sun Nonluminous an object that do not produce its own light and is visible due to reflected light eg a tree Sources of light ID: 615967 Download Presentation

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energy light electric bulb light energy bulb electric produced incandescent atoms gas mercury fluorescent emitted object visible result phosphor

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Slide1

Types of Light Emissions

Luminous: an object that emits/produces its own light (eg. sun)Non-luminous: an object that do not produce its own light and is visible due to reflected light (eg. a tree)Slide2

Sources of light

Light energy comes from different sources:NaturalArtificialSlide3

Incandescence

light emitted from a material (tungsten metal) because of the high temperature of the materialAbout 5% of the electrical energy used in an incandescent bulb becomes light, the rest is lost as heatSlide4

Light of electric discharge

process of producing light by passing an electric current through a gas (eg. a neon sign is red-orange; lightning)Slide5

Luminescence

The emission of light by a material or an object that has not been heated (eg. fluorescence)Light from fluorescenceProcess of emitting light while receiving energy from another sourceSlide6

How does a fluorescent bulb work?

It is an electric discharge tubeThe bulb contains mercury vapour along with an inert gas (Argon). The inside of the bulb is coated with a powdery substance called phosphorAs electrons travel through the gas, from one electrode to the other, they collide with atoms of mercury and excite these atomsSlide7

How does a fluorescent bulb work?

The excited mercury atoms release their excess energy in the form of ultraviolet (UV) light (humans can’t see this)The energy of the UV light is absorbed by the phosphor, which emits visible lightThese light bulbs are 20% efficient, meaning 20% of the energy it uses is converted into lightSlide8

Phosphorescence

Light that is emitted due to exposure of the source to white light, and that continues to be emitted for some time in the absence of the white light (eg. glow in the dark objects)Slide9

Chemiluminescence

Light that is produced by a chemical reaction without a rise in temperature (eg. glow stick)Slide10

Bioluminescence

Light that is produced by a biochemical reaction in a living organism (eg. firefly)Slide11

Triboluminescence

Production of light from friction as result of scratching, crushing, or rubbing certain crystals Light emitting diode (LED)Light produced as a result of an electric current flowing in semiconductors; no filaments and does not produce much heat (eg. Christmas lights)Slide12

Review questions

1) What do all incandescent materials have in common to cause them to emit light?2) What percentage of electrical energy used in an incandescent light bulb is converted to light?3) How is the ultraviolet radiation produced in a fluorescent light transformed into visible light?Slide13

4) What is phosphorescence?

5) Why is chemiluminescence sometimes referred to as cool light?6) What are two differences between LEDS and incandescent bulbs?

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