what is light? form of energy (first basic principle of light) that you can see radiates (spreads...
TRANSCRIPT
WHAT IS LIGHT?
• Form of energy (first basic principle of light) that you can see
•Radiates (spreads out) in all directions
•Light travels in a straight line unless it hits something or is pulled by gravity
•Light can be converted to different forms of energy like heat (thermal), electricity, or
chemical energy (photosynthesis)
CONVERSION TO THERMAL ENERGY
• The greenhouse effect
Light energy enters the greenhouse, hits objects and gets converted to thermal
energy which can’t get back out so heat builds up
This is a good thing
Green house gases, eg, CO2, trap more of the sun’s energy
increasing global temperatures
Too much of a good thing =
GLOBAL WARMING
WHERE DOES LIGHT COME FROM? - SOURCES OF LIGHT
• Natural light comes from the sun
• Artificial light can come from a variety of sources
1. Incandescent
2. Phosphorescent
3. Fluorescent
4. Chemiluminescent
5. Bioluminescent
NATURAL LIGHT
Light from the sun is produced by billions of nuclear reactions producing unimaginable amounts of energy
Visible light is only one form of energy that the sun provides
Other forms of energy from the sun are invisible and include radio waves, infrared waves,
ultraviolet, x-rays and gamma rays
INCANDESCENT LIGHT
Examples are a candle flame
And an ordinary light bulb
Visible light is produced by heating something to an extremely high temperature
Electrical energy Thermal energy Visible light energy
Phosphorescent
Absorption of light and then that light is radiated back out later
Many glow in the dark toys are made with paints, dyes and inks that phosphoresce
Watch painted with phosphorescent ink
Same watch, lights out Same watch, about 10 minutes later
FLUORESCENTAn example of this type of light is the fluorescent light bulb
The special phosphor coating inside the bulb absorbs the
ultraviolet energy given off by the mercury gas
The phosphor coating then glows
with visible light energy
Much more efficient than an incandescent light
source because there is not as much heat
produced
THE NORTHERN LIGHTS – AURORA BOREALIS
Very fast moving electrons in solar winds coming from the sun enter the earth’s atmosphere and collide with gaseous
particles releasing energy in the form of light
CHEMILUMINESCENT
Energy for light comes from a chemical reaction
BIOLUMINESCENT
Fireflies
Marine animals
A cloud of bioluminescent
marine organisms seen from space
An aura given off by bioluminescent water organisms
Chemiluminescence in living organisms
LIGHTING TECHNOLOGY AND SOCIETY – LEDs
LED = light emitting diode
Light is generated by the energy given off as millions of tiny negatively charged
particles bounce around inside a small device called a diode
LEDs use less electricity, last longer and do not produce as
much heat as incandescent light bulbs
LIGHTING TECHNOLOGY AND SOCIETY – FIBRE OPTICS
Light is transmitted along bundles of tiny tubes
Inside the tiny tubes, light cannot escape, it is constantly internally reflected
Telephone signals
Cable signals
Internet signals