Principles of Physics
Unit 16 Notes
Light & Color
Electromagnetic SpectrumThe range of electromagnetic waves extending from radio waves to gamma rays. (pg. 408)
Electromagnetic waveA wave that is partially electric and partially magnetic and carries energy. Emitted by vibrating electric charges. (pg. 408)
InfraredElectromagnetic waves of frequencies lower than the red of visible light. (pg. 408)
Light-yearThe distance light travels through a vacuum in one year. (pg. 407)
OpaqueTerm applied to materials that absorb light without reemission, and consequently do not allow light through them. (pg. 411)
PenumbraA partial shadow that appears where light from part of the source is blocked and light from another part of the source is not blocked. (pg. 412)
PhotonIn the particle model of magnetic radiation, a particle that travels only at the speed of light and whose energy is related to the frequency of the radiation in the wave model. (pg. 405)
PolarizationThe aligning of vibrations in a transverse wave, usually by filtering out waves of other directions.
(pg. 414)
RayA thin beam of light. (pg.412)
ShadowFormed where light rays can not reach. Sharp shadows are formed by small light source near object or larger light source from a longer distance. (pg.412)
TransparentMaterial that allows light to pass through. (pg. 409)
UltravioletElectromagnetic waves of frequencies higher that those of violent. (pg. 408)
UmbraA total shadow; the darker part of a shadow where all the light is blocked.(pg. 412)
Additive primary colorsRed, green, and blue because when lights of these colors are mixed the result is white light. (pg. 427)
Complementary colorsTwo colors of light beams that when added together appear white. (pg. 428)
line spectrumPattern of distinct lines of color, corresponding to particular wavelengths, that are seen in a spectroscope when a hot gas is viewed. (pg. 437)
PigmentA material that selectively selectively absorbs colored light. (pg. 424)
ScatterTo absorb sound or light and reemit it in all directions. (pg. 432)
SpectroscopeAn instrument used to separate the light from a hot gas or other light source into its constituent frequencies. (pg. 437)
SpectrumFor sunlight and other white light, the spread of colors seen when the light is passed through a prism or diffraction grating. In general, the spread of radiation by frequency, so that each frequency appears at a different position. (pg. 421)
Subtractive primary colorsThe colors of magenta, yellow, and cyan. These are the three colors most useful in clor mixing by subtraction. (pg. 430)
White Lightlight, such as sunlight, that is a combination of all the colors. Under white light, white appears white and colored objects appear in their individual colors. (pg. 421)