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 - In vacuum, it's commonly denoted as c, and it's a universal physical constant. It's value is exactly 299,792,458 meters per second.