Electromagnetic Spectrum - the range of electromagnetic waves extending from radio waves to gamma rays.
Electromagnetic Wave - a wave that is partly electric and partly magnetic and carries energy. Emitted by vibrating electric charges.
infrared - electromagnetic waves of frequencies lower than the red of visible light.
light year - the distance light travels through a vacuum during one year.
polarization - the aligning of vibrations in a transverse wave, usually by filtering out waves of other directions.
ray - a thin beam of light.
ultraviolet - electromagnetic waves of frequencies higher than those of violet light.
speed of light - the distance light can travel in a unit of time through a given substance. Light travels through a vacuum at 300,000 kilometers per second.