Chapter 13 - Waves and Sound

wave

A disturbance or vibration propagated from point to point in a medium or in space

natural frequency

A frequency at which an elastic object naturally tends to vibrate, so that minimum energy is required to produce a forced vibration or to continue vibrating at that frequency

sound wave

A longitudinal vibratory disturbance that travels in a medium, which can be heard in the approximate frequency range 20-20,000 Hz

beats

A series of alternate reinforcements and cancellations produced by the interference of two waves of slightly different frequency, heard as a throbbing effect in sound waves

standing wave

A stationary wave pattern formed in a medium when two sets of identical waves pass through the medium in opposite directions

longitudinal wave

A wave in which the medium vibrates in a direction parallel to the direction in which the wave travels

transverse wave

A wave in which the medium vibrates in a direction perpendicular to the direction in which the wave travels. Light is an example

frequency

For a vibrating body or medium, the number of vibrations per unit time. For a wave, the number of crests that pass a particular point per unit time

amplitude

For a wave or vibration, the maximum displacement on either side of the equilibrium (midpoint) position

hertz

The SI unit of frequency. It equals one vibration per second

bow wave

The V-shaped wave produced by an object moving across a liquid surface at a speed greater than the wave speed

refraction

The bending of a wave through either a non-uniform medium or from one medium to another, caused by difference in wave speed

Doppler effect

The change in frequency of wave motion resulting from motion of the wave source or receiver

shock wave

The cone-shaped wave created by an object moving at supersonic speed through a fluid

wavelength

The distance between successive crests, troughs, or identical parts of a wave

sonic boom

The loud sound resulting from the incidence of a shock wave

interference

The pattern formed by superposition of different sets of waves that produces mutual reinforcement in some places and cancellation in others

wave speed

The speed with which waves pass a particular point: _________ = frequency x wavelength

resonance

The response of a body when a forcing frequency matches its natural frequency

forced vibration

The setting up of vibrations in an object by a vibrating force

period

The time required for a vibration or a wave to make a complete cycle; equal to 1/frequency