Waves

Wave: A disturbance that is transmitted from one place to the next with no actual transport of matter.

All waves start with a vibration.All waves carry energy.

Transverse wave: a wave with vibration at right angles to the direction the wave is traveling.

Longitudinal wave: A wave in which the vibration moves in the same direction that the wave is traveling.

Water wave

Period: The time required to complete a single cycle or vibration. Symbol: T

Frequency: The number of cycles or vibrations per unit of time. Symbol: f

Frequency = 1/periodOrf =

Hertz: A unit of frequency equal to one cycle per second.

1

T

Mechanical wave: A wave that travels by the motion of particles in a medium.

Can be transverse (violin string) or longitudinal (sound).

Cannot travel through a vacuum.

Electromagnetic wave: A wave made of electric and magnetic fields. electromagnetic waves can travel through a vacuum and do not need a medium.

Examples: light, radio waves, microwaves, X-rays.

All electromagnetic waves are transverse.

Parts of a wave:

Wavelength: The distance from crest to crest of a wave. Symbol: λ (lambda).

Crest: A high point on a wave.

Trough: A low point on a wave.

Amplitude: The maximum displacement from the midpoint of a wave or vibration.

Pulse wave: A wave that consists of a single traveling pulse.

Periodic wave: A wave produced by periodic motion.

Damping: When the amplitude of a wave diminishes over time as energy is dissipated.

Constructive interference: when the crest of one wave overlaps the crest of another and their individual effects add together.

Another look at constructive interference:

Destructive interference: When the crest of one wave overlaps with the trough of another and their effects are reduced.

Interference pattern: A regular arrangement of places where wave effects are increased, decreased, or neutralized.

Standing Wave: A wave that appears to stay in one place.

Node: A stationary point on a standing wave.Antinode: The positions on a standing wave where

the largest amplitudes occur.

Doppler effect: The apparent change in frequency of a wave due to the motion of the source or the receiver.

Pitch: How high or low a sound frequency appears to be.

Compression: A pulse of compressed air; part of a sound wave.

Rarefaction: A disturbance in air in which the pressure is lowered; part of a sound wave.

Resonance: When the frequency of forced vibrations on an object matches the object’s natural frequency, and a dramatic increase in amplitude occurs.

Superposition principle: When two or more waves travel through a medium at the same time, the resultant wave is the sum of the displacements of the individual waves at each point.

Beats: The periodic variations in the amplitude of a wave that is the superposition of two waves of slightly different frequencies.

Intensity: The rate at which energy flows through an area perpendicular to the direction of wave motion.

Loudness: The sensation of sound intensity as perceived by the human ear. Loudness is not directly proportional to intensity. The relationship is approximately logarithmic.