Energy: The capacity or power to do work, such as the capacity to move an object (of a given mass) by the application of force.
Energy efficiency: Products or systems that use less energy to do the same or better job than conventional products or systems.
Waves: A regular disturbance (movement) up and down or back and forth a disturbance moving through a medium.
Amplitude: The maximum height of a wave, measured from the position of equilibrium.
Frequency: The number of waves passing a certain point within a given time period.
Wavelength: The distance between successive crests or troughs of a wave.
Sound: Vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.
Light: A type of energy. It is a form of electromagnetic radiation of a wavelength which can be detected by the human eye.
Normal: An imaginary line drawn at 90° to the surface of a mirror.
Reflection: Occurs when light changes direction as a result of "bouncing off" of a surface such as a mirror.
Refraction: Occurs when light changes direction when passing from one medium to another (i.e. gas to liquid).
Incidence: An incoming ray of light.
Concave: Having an outline or surface that curves inward like the interior of a cylinder or sphere.
Convex: Having an outline or surface curved like the exterior of a cylinder or sphere. Mirror: A reflective surface that reflects a clear image.
ROYGBIV: A mnemonic for the sequence of hues in the visible spectrum and in rainbows: Red, Orange, Yellow, Green, Blue. Indigo, and Violet.