Light & APPLICATIONS OF Optics

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. *

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.

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.

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)

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

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

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

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.

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

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.

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.

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.

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

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

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

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 *