1. Light & APPLICATIONS OF Optics

2. Light Light interacts with matter in 4 known ways.
It sometimes bounces off matter.
Sometimes it is absorbed by matter.
In some cases it passes through the matter.
Most times it bends as it encounters matter. *

3. What is Light?
Light is energy and travels in the form of a wave. We call them electromagnetic waves.
Light travels in straight lines unless another force acts upon it.

4. Electromagnetic Waves
Waves that carry electrical energy and magnetic energy.
An important characteristic of a wave is it’s wavelength. The wavelength of a wave is the distance between two peaks. It also determines the color of the light.

5. Types of Light Emission
Incandescence
Light given off by an object because it is very hot.
Ex. incandescent light bulb (old style light bulb, very inefficient, 90% heat, 10% light, filament 3000°C)

6. Luminescence Light given off by an object that has not been heated.
Chemiluminescence
is light that is release during chemical reactions
Ex. glow sticks
Bioluminescence
Is a form of Chemiluminescence that occurs in living organisms.
Ex. fireflies

7. Electrical Discharge
occurs in a sealed glass tube containing one or more gases.
Electricity travels from one end to the other bumping into particles of gas, giving them energy.
The gases release this energy as light.
Ex. street lights

8. Fluorescence
is a form of electric discharge. But these gases emit ultraviolet light.
the walls of the glass tube are covered with a substance called a phosphor.
The ultraviolet light transfers energy to the phosphor, which then releases the energy as light
Ex. lights in the ceiling

9. Electromagnetic Spectrum
a representation of the types of electromagnetic waves arranged according to wavelength
The only waves of the electromagnetic spectrum that you can see are those of visible light.
The longest waves of visible light are red and the shortest are violet.

11. Behavior of Light Reflection
the process in which light "bounces off“ the surface of an object and travels in another direction
Absorption
the process in which light energy remains in the object that it hits, and the light energy is converted into heat
Transmission
the process in which light travels through an object and continues travelling

12. Properties of Matter wrt Light
Transparent
A property of an object that allows light to penetrate it, making it possible to see objects from the other side.
Translucent
A property of an object that allows light to pass through but scatters it in different directions.
Opaque
A property of an object that will not allow any light to penetrate it.

13. Color of Opaque Objects
The color of opaque objects depends on what light they reflect.
White objects reflect all colors of the visible spectrum.
Black objects absorb all colors of the visible spectrum.
Blue objects absorb all colors except blue.
Some objects reflect mostly one color but a little of some others creating shades of a color.

14. Color of Translucent or Transparent Objects
For a transparent or translucent object to have a certain color, it must absorb all other colors of light
It must also transmit and reflect the color that is its particular color.

15. Color Additive Primary Colors
to add colors, you need sources of colored lights that can reach an observer's eyes.
primary additive colors are red, green and blue
overlapping all 3 produces white

16. overlapping 2 produces secondary colors
secondary additive colors are cyan, magenta and yellow
Red + Green = Yellow
Red + Blue = Magenta
Green + Blue = Cyan *

17. Subtractive Primary Colors
when an object absorbs a color, it removes it from the beam of light or subtracts it
Most of the color we see is the result of subtractive colors.
primary subtractive colors are cyan, magenta and yellow.
overlapping all 3 produces the color black

18. White – (Cyan + Magenta) = Blue White – (Cyan + Yellow) = Green
subtracting equal amounts of two of the three subtractive primary colors make secondary colors
secondary subtractive colors are the same as the primary additive colors, Red, Green and Blue
White – (Cyan + Magenta) = Blue
White – (Cyan + Yellow) = Green
White – (Magenta + Yellow) = Red *