1. LIGHT ENERGY & ITS SOURCES
Section 10.1

2. Discuss the following and are ready to give answers when prompted:
In groups
Discuss the following and are ready to give answers when prompted:
What are the sources of light?
How does a light bulb work?
What does luminous and non-luminous mean?
How is a shadow formed?
What does transparent, translucent and opaque mean?
Electricity passes through the filament and its starts to get hot and glows.
GIVES OFF LIGHT (EMITS) REFLECTS LIGHT
A SOLID OBJECTS BLOCK THE LIGHT
Can see through can see some light light cant get through

3. Light Light is a form of energy that can be detected by the human eye
Light energy comes from both natural and artificial sources
Light travels directly from a luminous source (object that emit light) or indirectly from a non-luminous source (object reflects light) to your eyes

4. Electrical energy → light energy + thermal energy
Incandescence
Emitting light because of high temperatures
Kerosene lamp uses chemical energy to transform into heat and light.
electricity passes through a tungsten wire in a bulb making it so hot that it glows
Inefficient - since much of the input energy becomes thermal (heat) energy
Electrical energy → light energy + thermal energy

5. Luminescent
an emission of light by a substance not resulting from heat

6. Electric Discharge
Electric discharge is the process of emitting light because of electricity passing through a gas
Examples: Lightning, neon signs

7. Phosphorescence
Materials called phosphors store light energy and release it again as light energy
Phosphorescence is the process of emitting light for a short time after receiving energy from another source

8. Fluorescence
Fluorescence is the process of emitting light while receiving energy from another source Ex. Fluorescent light tubes Fluorescence is a combination of two different light sources, electric discharge and phosphorescence
Electricity passes along the tube and causes particles of mercury vapour to emit invisible ultraviolet (UV) energy.
The UV energy is absorbed by the phosphor coating on the inside of the tube, which then emits light energy.

9. Chemiluminescence
Chemiluminescence is the process of changing chemical energy into light energy with little or no change in temperature

10. Bioluminescence
Bioluminescence is when chemiluminescence is used in living things

11. Luminescent Incandescent
Visible Light
Luminescent
(emits light without heat)
Incandescent
(emit light because of heat)
Phosphorescent
Chemiluminescent
Candlelight
Electric Discharge
Glow-in-dark
stickers
Bioluminescent
neon signs
Fluorescent
firefly
glow sticks
fluorescent bulbs
Activity: Create a concept map of the different sources of light breaking them down from visible light to examples.

12. Sources of Light
What factors should be considered when choosing a light source?
Brightness
Location
Attractiveness
Cost
Efficiency (how well the light source transforms input energy into light energy)
Project: Create an advertisement promoting a source of light