Sources of Light (slide 3) Flashcards
Light enters our eyes from
ALL objects
Two types of objects
luminous and non luminous
luminous
produces it’s own light
non luminous
does not produce it’s own light (can only be seen by reflected light)
Technologies can produce light by
converting other forms of
energy into forms of light
There are many forms of energy that is converted
Chemical energy
Electrical energy
Nuclear energy
Thermal energy
common sources of light include
incandesecense
light from electric discarge
luminessceneces
fluoressense
phophorescence
chemilumuminscene
light emitting (diod)
Incandescence
The production of light as a result of high temperature
Incandescence is
Inefficient (more heat) (10% of it is light)
Heat 🡪 light
Incandescent light bulb
Electrical energy 🡪 heat + light (light bulb)
Fuel-burning technologies
Chemical energy 🡪 heat + light (lighter)
Light from Electric Discharge
The process of producing light by the build up and quick transfer of
electrons between two objects
The process of producing light by an electric current flowing through gas
Lightning
massive charge build up of charge-charge will want to lose charge to (discarge)
Luminescence
Light generated without heating the object
The energy used to excite the atoms comes from a variety of sources
(Luminescence)
Fluorescence
Visible light that is emitted immediately after exposure to
ultraviolet light
Efficient
Phosphorescence
Visible light that is emitted gradually after exposure to ultraviolet
light
UV radiation 🡪 light
Re emit it over a long period of time
Chemiluminescence
Light that is generated by the energy released in a chemical reaction without a
rise in temperature
Chemical energy 🡪 light (glow stick)
Chemiluminescence
break the glow stick you break the a stick inside holding chemical hydrogen peroxide
causes light
Bioluminescence
Light is produced from a chemical reaction in living organisms
Chemical energy 🡪 light
Bioluminescence (examples)
Firefly and jelly fish
Triboluminescence
Light is produced when certain crystals are scratched, crushed, or
from vibration
MECHANICAL ENERGY
Mechanical energy 🡪 light
Triboluminescence
Light emitting DIOD
When electric current flowing through semi conducter is produced
Electtric energy-light
Describe the difference between luminous objects and non-luminous objects.
Luminous objects produce their own light.
Non-luminous objects do not produce their own light – only seen because they reflect
light
Describe how light is produced through incandescence. Provide one (1) example.
Light is produced through incandescence when an object is heated to high
temperatures (light produced with heat).
Fire is a source of incandescent light
Describe how light is produced through luminescence. Provide two (2) examples.
Light is produced through luminescence when an object converts energies other than
heat into light (light produced with little or no heat).
Chemiluminescence (glow sticks) produce light through chemicals reacting.
Fluorescence (light bulbs) produce energy through charging fluorescent particles
(which produces visible light) using UV light.
What is the main difference between fluorescence and phosphorescence?
Both fluorescence and phosphorescence absorb UV radiation to charge it’s particles
before visible light is emitted. The difference is that fluorescence releases all of the
energy as visible light immediately while phosphorescence gradually releases the
energy as visible over longer periods of time.
State two (2) reasons how/why living organisms might use bioluminescence.
Defensive Adaptation: confuse/evade predators
Offensive Adaptation: lure prey
Attraction: attract mates
- Explain why homeowners should switch from incandescent light bulbs to fluorescent or LED
light bulbs.
Fluorescent (and LED) light bulbs produce the same amount of light as incandescent
light bulbs, but use less energy to do so and has a longer lifetime than incandescent
bulbs.
