2Light 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. *
3What 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.
4Electromagnetic 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.
5Types of Light Emission IncandescenceLight 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)
6Luminescence Light given off by an object that has not been heated. Chemiluminescenceis light that is release during chemical reactionsEx. glow sticksBioluminescenceIs a form of Chemiluminescence that occurs in living organisms.Ex. fireflies
7Electrical Dischargeoccurs 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
8Fluorescenceis 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 lightEx. lights in the ceiling
9Electromagnetic Spectrum a representation of the types of electromagnetic waves arranged according to wavelengthThe 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.
11Behavior of Light Reflection the process in which light "bounces off“ the surface of an object and travels in another directionAbsorptionthe process in which light energy remains in the object that it hits, and the light energy is converted into heatTransmissionthe process in which light travels through an object and continues travelling
12Properties of Matter wrt Light TransparentA property of an object that allows light to penetrate it, making it possible to see objects from the other side.TranslucentA property of an object that allows light to pass through but scatters it in different directions.OpaqueA property of an object that will not allow any light to penetrate it.
13Color 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.
14Color of Translucent or Transparent Objects For a transparent or translucent object to have a certain color, it must absorb all other colors of lightIt must also transmit and reflect the color that is its particular color.
15Color 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 blueoverlapping all 3 produces white
16overlapping 2 produces secondary colors secondary additive colors are cyan, magenta and yellowRed + Green = YellowRed + Blue = MagentaGreen + Blue = Cyan*
17Subtractive Primary Colors when an object absorbs a color, it removes it from the beam of light or subtracts itMost 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
18White – (Cyan + Magenta) = Blue White – (Cyan + Yellow) = Green subtracting equal amounts of two of the three subtractive primary colors make secondary colorssecondary subtractive colors are the same as the primary additive colors, Red, Green and BlueWhite – (Cyan + Magenta) = BlueWhite – (Cyan + Yellow) = GreenWhite – (Magenta + Yellow) = Red*