- absorption: the taking in of light energy by an object
- compression: the part of the wave where particles are closest together
- echo: reflected sound
- frequency: the number of times a wave makes a complete cycle in a second
- gas: sound waves travel the slowest through these and light travels the quickest
- longitudinal waves: particles move side and parallel to a source
- opaque: describes materials that do not let any light pass through them
- pitch: a measure of whether a sound seems high or low, determined by the sound's frequency
- reflection: the bouncing back of a wave off an object's surface
- refraction: bending of light caused by the change of speed that occurs when light rays pass from one transparent medium to another
- solid: sound waves travel most quickly through these and light travels the slowest
- sound: a form of energy that travels in waves
- sound energy and light travel: through solids, liquids, and gases
- sound waves: travel outwards in all directions from the source
- translucent: describes materials that let some light rays pass through but scatter some of the other rays
- transparent: describes materials that let nearly all the light rays that hit them pass through
- transverse waves: particles move up and down and at right angles to a source
- wavelength: distance between one point on a wave to the next similar point on a wave