Unit 3B Physics Mechanical Waves and Sound

wave

a traveling oscillation that transfers energy from one point to another

Wave characteristics

frequency, amplitude, wavelength, speed, energy

mechanical wave

A wave that requires a medium through which to travel

electromagnetic waves

A form of energy that can move through the vacuum of space (does not need a medium)

transverse wave

A wave that moves the medium in a direction perpendicular to the direction in which the wave travels

longitudinal wave

A wave that moves the medium in a direction parallel to the direction in which the wave travels.

surface waves

A surface wave is a wave that travels along the surface of a medium

crest

a high point on a transverse wave

trough

the lowest point of a transverse wave

wavelength

Horizontal distance between points on wave (crests or trough or points of one cycle)

amplitude

total energy or height from equilibrium (rest position)

period

the time that it takes a complete cycle or wave oscillation to occur

frequency

the number of complete wavelengths that pass a point in a given time

compression

The part of a longitudinal wave where the particles of the medium are close together.

rarefaction

The part of a longitudinal wave where the particles of the medium are far apart

reflection

The bouncing back of a wave when it hits a surface through which it cannot pass.

Doppler effect

A change in frequency caused by motion of the sound source, motion of the listener, or both.

Interference

the combination of two or more waves that results in a single wave

constructive inference

the interference that occurs when two waves combine to take a wave with a larger amplitude

destructive inference

occurs when waves add up to make a smaller amplitude (compressions align w rarefactions)

standing wave

a wave that appears to stand in one place, even though it is really two waves interfering as they pass through each other

node

A point on a standing wave that has no motion aka amplitude (resting)

antinode

A point of maximum amplitude on a standing wave

pitch

a tone's experienced highness or lowness; depends on frequency

volume

loudness of sound depending on sound waves amplitude

infrasound

Sound waves with frequencies below 20 Hz.

ultrasound

Sound waves with frequencies above 20,000 Hz.

How does air temperature affect the speed of sound?

when warm: more vibrations occur (more energy)

when cold: less vibrations occur (less energy)faster

inwarm air

speed of sound

depends on tension of medium and elasticity (ability to snap back into shape after disturbance)

why is sound a wave

has all properties of a wave (ie: frequency, amplitude, wavelength, speed, transfers energy)

harmonics

different patterns of nodes and antinodes created by multiples of frequency fundamentals

Law of Superposition

the amplitude of the resulting wave is always equal to the sum of the amplitude of the individual waves

units of frequency

Hertz (Hz)

units of period

time (seconds)

parts of a transverse wave

crest, trough, wavelength, amplitude

parts of a longitudinal wave

compression, rarefaction, wavelength

relationship between wavelength and frequency

Inversely related--as one increases, the other decreases

amplitude and energy

directly related (higher the amplitude, the greater the energy)

frequency and energy

directly related (higher the frequency, the greater the energy

speed of sound in solids

fastest

speed of sound in liquid

faster than in air

speed of sound in gas

depends on temperature of the gas and mass of particles

speed of sound in air

increases as air temperature increases

Wave speed equation

Doppler equation

simple harmonic motion

vibration about an equilibrium position in which a restoring force is proportional to the displacement from equilibrium

Period of a pendulum equation

Period-Frequency Relationship

speed of sound in air equation

harmonic frequency - two open or two closed ends

harmonic frequency - one open, one closed end