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 then 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 bean of light.
ultraviolet: electromagnetic waves of frequencies higher then those of violet light.
speed of light: the speed at which light travels in a vacuum