Absorb To take in energy, such as light or sound, and transform it into another type of energy, such as heat or motion.

Amplitude A wave's intensity; the maximum distance a wave carries the particles of a medium from its original position.

Electromagnetic Spectrum The entire range of frequencies and wavelengths of light energy.

Electromagnetic Wave (or Light Wave) A disturbance that can carry energy from one place to another, through either a medium or a vacuum.

Energy The ability to do work. Examples of energy include light, sound, heat and electricity.

Frequency The number of waves produced during a given amount of time.

Mechanical Wave A disturbance that carries energy from one place to another through a medium--a liquid, solid or gas.

Medium Matter--such as a liquid, gas or solid--that waves carry energy through.

Particle A minute, or tiny, portion of matter.

Reflect To bounce off.

Refract To change direction when moving through one medium into another.

Transverse Wave A wave in which the particles of the medium move in a direction perpendicular to the direction the wave itself is moving.

Wave A disturbance that carries energy from one place to another.

Wavelength The distance between any point on a wave to an identical point on the next wave.