heat and wave

acoustic impedance

property of medium that makes the propagation of sound waves more difficult

antinode

point of maximum displacement

bow wake

V-shaped disturbance created when the wave source moves faster than the wave propagation speed

Doppler effect

an alteration in the observed frequency of a sound due to motion of either the source or the observer

Doppler shift

the actual change in frequency due to relative motion of source and observer

Doppler-shifted ultrasound

a medical technique to detect motion and determine velocity through the Doppler shift of an echo

fundamental

the lowest-frequency resonance

harmonics

the term used to refer collectively to the fundamental and its overtones

hearing

the perception of sound

infrasound 

sounds below 20 Hz

intensity

the power per unit area carried by a wave

intensity reflection coefficient

a measure of the ratio of the intensity of the wave reflected off a boundary between two media relative to the intensity of the incident wave

loudness 

the perception of sound intensity

node

point of zero displacement

note

basic unit of music with specific names, combined to generate tunes

overtones

all resonant frequencies higher than the fundamental

phon

the numerical unit of loudness

pitch

the perception of the frequency of a sound

sonic boom 

a constructive interference of sound created by an object moving faster than sound

sound 

a disturbance of matter that is transmitted from its source outward

sound intensity level

a unitless quantity telling you the level of the sound relative to a fixed standard

sound pressure level

the ratio of the pressure amplitude to a reference pressure

timbre/tone

number and relative intensity of multiple sound frequencies

ultrasound

sounds above 20,000 Hz

amplitude

the maximum displacement from the equilibrium position of an object oscillating around the equilibrium position

antinode

the location of maximum amplitude in standing waves

beat frequency

the frequency of the amplitude fluctuations of a wave

constructive interference

when two waves arrive at the same point exactly in phase; that is, the crests of the two waves are precisely aligned, as are the troughs

critical damping

the condition in which the damping of an oscillator causes it to return as quickly as possible to its equilibrium position without oscillating back and forth about this position

deformation

displacement from equilibrium

destructive interference

when two identical waves arrive at the same point exactly out of phase; that is, precisely aligned crest to trough

elastic potential energy

potential energy stored as a result of deformation of an elastic object, such as the stretching of a spring

force constant

a constant related to the rigidity of a system: the larger the force constant, the more rigid the system; the force constant is represented by k

frequency

number of events per unit of time

fundamental frequency

the lowest frequency of a periodic waveform

intensity

power per unit area

longitudinal wave

a wave in which the disturbance is parallel to the direction of propagation

natural frequency

the frequency at which a system would oscillate if there were no driving and no damping forces

nodes

the points where the string does not move; more generally are where the wave disturbance is zero in a standing wave

oscillate

moving back and forth regularly between two points

over damping

the condition in which damping of an oscillator causes it to return to equilibrium without oscillating; oscillator moves more slowly toward equilibrium than in the critically damped system

overtones

multiples of the fundamental frequency of a sound

period

time it takes to complete one oscillation

periodic motion

motion that repeats itself at regular time intervals

resonance

the phenomenon of driving a system with a frequency equal to the system's natural frequency

resonate

a system being driven at its natural frequency

restoring force

force acting in opposition to the force caused by a deformation

simple harmonic motion

the oscillatory motion in a system where the net force can be described by Hooke’s law

simple harmonic oscillator

a device that implements Hooke’s law, such as a mass that is attached to a spring, with the other end of the spring being connected to a rigid support such as a wall

simple pendulum

an object with a small mass suspended from a light wire or string

superposition

the phenomenon that occurs when two or more waves arrive at the same point

transverse wave

a wave in which the disturbance is perpendicular to the direction of propagation

under damping

the condition in which damping of an oscillator causes it to return to equilibrium with the amplitude gradually decreasing to zero; system returns to equilibrium faster but overshoots and crosses the equilibrium position one or more times

wave

a disturbance that moves from its source and carries energy

wave velocity

the speed at which the disturbance moves. Also called the propagation velocity or propagation speed

wavelength

the distance between adjacent identical parts of a wave

adiabatic process

a process in which no heat transfer takes place

Carnot cycle

a cyclical process that uses only reversible processes, the adiabatic and isothermal processes

Carnot efficiency

the maximum theoretical efficiency for a heat engine

Carnot engine

a heat engine that uses a Carnot cycle

change in entropy

the ratio of heat transfer to temperature Q/T

coefficient of performance

for a heat pump, it is the ratio of heat transfer at the output (the hot reservoir) to the work supplied; for a refrigerator or air conditioner, it is the ratio of heat transfer from the cold reservoir to the work supplied

cyclical process

a process in which the path returns to its original state at the end of every cycle

Entropy

a measurement of a system's disorder and its inability to do work in a system

first law of thermodynamics

states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system

heat engine

a machine that uses heat transfer to do work

heat pump

a machine that generates heat transfer from cold to hot

human metabolism

conversion of food into heat transfer, work, and stored fat

internal energy

the sum of the kinetic and potential energies of a system’s atoms and molecules

irreversible process

any process that depends on path direction

isobaric process

constant-pressure process in which a gas does work

isochoric process

a constant-volume process

isothermal process

a constant-temperature process

macrostate

an overall property of a system

microstate

each sequence within a larger macrostate

Otto cycle

a thermodynamic cycle, consisting of a pair of adiabatic processes and a pair of isochoric processes, that converts heat into work, e.g., the four-stroke engine cycle of intake, compression, ignition, and exhaust

reversible process

a process in which both the heat engine system and the external environment theoretically can be returned to their original states

second law of thermodynamics

heat transfer flows from a hotter to a cooler object, never the reverse, and some heat energy in any process is lost to available work in a cyclical process

second law of thermodynamics stated in terms of entropy

the total entropy of a system either increases or remains constant; it never decreases

statistical analysis

using statistics to examine data, such as counting microstates and macrostates

conduction

heat transfer through stationary matter by physical contact

convection

heat transfer by the macroscopic movement of fluid

emissivity

measure of how well an object radiates

greenhouse effect

warming of the Earth that is due to gases such as carbon dioxide and methane that absorb infrared radiation from the Earth’s surface and reradiate it in all directions, thus sending a fraction of it back toward the surface of the Earth

heat

the spontaneous transfer of energy due to a temperature difference

heat of sublimation

the energy required to change a substance from the solid phase to the vapor phase

kilocalorie

1 kilocalorie = 1000 calories

latent heat coefficient

a physical constant equal to the amount of heat transferred for every 1 kg of a substance during the change in phase of the substance

mechanical equivalent of heat

the work needed to produce the same effects as heat transfer

net rate of heat transfer by radiation

R factor

the ratio of thickness to the conductivity of a material

Radiation

heat transfer which occurs when microwaves, infrared radiation, visible light, or other electromagnetic radiation is emitted or absorbed; energy transferred by electromagnetic waves directly as a result of a temperature difference

rate of conductive heat transfer

rate of heat transfer from one material to another

specific heat

the amount of heat necessary to change the temperature of 1.00 kg of a substance by 1.00 ºC

Stefan-Boltzmann law of radiation

where sigma is the Stefan-Boltzmann constant, A is the surface area of the object, T is the absolute temperature, and e is the emissivity

sublimation

the transition from the solid phase to the vapor phase

thermal conductivity

the property of a material’s ability to conduct heat

absolute zero

the lowest possible temperature; the temperature at which all molecular motion ceases

Avogadro’s number

the number of molecules or atoms in one mole of a substance (units are particles/mole)