Grade 12 Physics Chapter 6 Flashcards

Vocabulary practice flashcards covering wave mechanics, sound characteristics, intensity, the Doppler effect, and ultrasound applications from Chapter 6 of Grade 12 Physics.

Wave

A disturbance that travels in a medium (or vacuum for electromagnetic waves) transferring energy and momentum from one place to another without large-scale motion of the medium itself.

Interference

The addition of two or more waves which pass the same point in space simultaneously.

Destructive Interference

Occurs when two waves combine such that crest meets trough and trough meets crest, causing them to cancel one another.

Constructive Interference

Occurs when two waves combine such that crest meets crest and trough meets trough, resulting in a wave of double the original amplitude.

Beats

The fluctuations in intensity or loudness that occur when two sound waves of slightly different frequencies interfere with each other.

Beat frequency

The difference between two original frequencies, calculated as $n = f_1 - f_2$ (f_1 > f_2) or $n = f_2 - f_1$ (f_2 > f_1).

Sound

A pressure variation that propagates through a medium as a longitudinal wave, causing air molecules to move in the direction of propagation.

Infrasound

Sound with frequencies lower than $20\,\text{Hz}$, which cannot be heard by humans.

Ultrasound

Sound waves with frequencies greater than $20\,\text{kHz}$ ($20,000\,\text{Hz}$).

Pitch

A characteristic of sound that depends upon the frequency of sound waves: lower frequency results in lower pitch, while higher frequency results in higher pitch.

Loudness

A subjective sensation produced by sound depending on a person's hearing ability, measured in units called "phon" or decibels ($dB$).

Quality (Timbre)

The characteristic of sound determined by the number of overtones present, allowing listeners to distinguish between different sources at the same pitch and loudness.

Young’s modulus ($Y$)

A measure of the stiffness of a solid used to calculate the speed of sound in solids according to the formula $v = \sqrt{\frac{Y}{\rho}}$.

Bulk modulus ($B$)

A measure of the compressibility of a fluid (liquid or gas) used to calculate the speed of sound via the formula $v = \sqrt{\frac{B}{\rho}}$.

Intensity of sound ($I$)

Defined as the rate of flow of energy per unit area perpendicular to the direction of the wave, measured in Watts per square meter ($\text{W\,m}^{-2}$).

Threshold of hearing ($I_0$)

The minimum intensity of a sound wave required to be audible to humans, valued at approximately $10^{-12}\,\text{W\,m}^{-2}$ at $1000\,\text{Hz}$ ($0\,dB$).

Inverse Square Law

A relationship stating that the intensity of sound is inversely proportional to the square of the distance ($d$) from the source ($I \propto \frac{1}{d^2}$).

Decibel ($dB$)

A logarithmic unit of measurement used to express the intensity level ($\beta$) of sound, where $\beta = 10 \log\left(\frac{I}{I_0}\right)$.

Sonic boom

An explosive noise associated with shock waves created when an object travels through the air faster than the speed of sound.

Shock wave

A large wave disturbance created when an object moves at the speed of sound and successive wave fronts pile up on one another.

Doppler effect

The apparent change in frequency of a sound caused by the relative motion between the source and the observer.

Transducer

A device that converts energy from one form to another, such as converting electrical energy into ultrasound waves.

Echo

A reflected sound that can be distinguished from the original because it arrives after a delay of at least $0.10\,\text{s}$.

Reverberation

The mixing of many reflected sounds with the original sound, occurring when reflected sound arrives before $0.10\,\text{s}$, perceived as an increase in volume.

Ultrasonography

A medical application of echoes used to image and determine the state of various organs inside a human body.

Echocardiography

An application of echo techniques specifically used to determine the functioning and action of the heart.