Two common physics principles are sound and light waves. Sound waves are pressure variations that are transmitted through matter. The speed at which sound travels depends on temperature and the medium (air) in which the sound waves travel. Here are a few sound wave highlights:

• When sound waves hit a hard surface, they reflect off it, causing an echo.

• The number of compressions by sound waves that occur in one second is called the frequency or pitch of the sound.

• If the source of the sound is in motion (such as a car coming down the street), you hear or perceive sound of higher or lower frequencies. This sensation is because of the Doppler effect.

Light waves can be visible or nonvisible. A light wave is measured in terms of its wavelength, or how far it travels before the wave’s shape repeats itself. If you know the distance between repeating corresponding points of the same phase of the wave, you can figure out wavelength.

The wavelength

of a sinusoidal waveform (a smooth succession of curves) traveling at the speed of light v (about 3 x 108 meters per second) is given by

where f is the wave’s frequency.