Question 1

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields

Accepted Answer

The integral of the intensity of sound over any Gaussian surface that encloses the source yields a conserved quantity, which is the total power output by the source. This is because sound intensity is a measure of the power per unit area, and integrating this over a closed surface captures the total power emitted by the source, which is conserved as it passes through the surface.

Question 2

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields

Accepted Answer

The integral of the intensity ($I$) of sound over a surface area ($dA$) that encloses the source ($\int I dA$) gives the total power ($P$) radiating from the source. This is because sound intensity is defined as power per unit area ($I = P/A$), so when you integrate intensity over an area that encloses the source, you essentially calculate the total power emitted by the source.

Question 3

You are in a dark cave; suddenly you hear screeching sounds that are increasing in pitch. From this you discern that something is

Accepted Answer

The increasing pitch of the screeching sounds indicates that the source of the sound is coming toward you, due to the Doppler effect, which causes the frequency of sound waves to increase as the source moves closer to the observer.

Question 4

If the pitch of the sound is increasing, then the wavelength

Accepted Answer

The pitch of a sound is directly related to its frequency. As the pitch increases, the frequency of the sound waves increases. Since the speed of sound in a given medium is constant, an increase in frequency results in a decrease in wavelength. Therefore, if the pitch of the sound is increasing, the wavelength is decreasing.

Question 5

For any sound wave traveling in a medium, as the frequency is increased, the following remains constant:

Accepted Answer

The velocity of a sound wave in a medium is determined by the properties of the medium (such as its density and elasticity) and does not change with the frequency of the sound.

Question 6

The speed of sound in air v depends on the air pressure p and the air density as

Accepted Answer

The speed of sound in air $v$ is directly proportional to the square root of the ratio of pressure $p$ to density $\rho$, which is mathematically represented as $v \propto \sqrt { \frac { p } { \rho } }$. This relationship is derived from the equation for the speed of sound in a medium, where the speed of sound increases with an increase in the medium's stiffness (pressure) and decreases with an increase in its density.

Question 7

The speed of water waves in deep water depends on the two parameters

Accepted Answer

The speed of water waves in deep water primarily depends on gravity and the wavelength of the waves. Gravity acts as the restoring force, and the wavelength determines the speed at which the wave energy travels.

Question 8

The speed of water waves in shallow water depends on the two parameters

Accepted Answer

In shallow water, the speed of water waves primarily depends on gravity and the depth of the water. The shallower the water, the slower the waves travel, because the wave speed is directly influenced by the gravitational pull and the depth of the water body.

Question 9

Audible sound waves have wavelengths in air on the order of

Accepted Answer

Audible sound waves typically have wavelengths ranging from a few inches to a few feet in air, correlating with the frequencies humans can hear (approximately 20 Hz to 20 kHz). The speed of sound in air is about 343 meters per second, and wavelength is related to the speed of sound and frequency by the equation wavelength = speed/frequency.

Question 10

The speed of sound in air (in meters per second) is on the order of

Accepted Answer

The speed of sound in air at room temperature is approximately 343 meters per second, which is on the order of 300 (C).

Question 11

Diffraction is observed around an obstacle of size $\approx$ 20 $\lambda$ . If the obstacle is reduced in size to $\approx$ 2 $\lambda$ , the diffraction effect

Accepted Answer

Diffraction effects increase when the size of the obstacle or aperture approaches the wavelength of the wave. Reducing the obstacle size to about 2λ, closer to the wavelength, enhances the diffraction observed.

Question 12

All of the following "pairs" are measured or expressed in terms of a logarithmic scale except

Accepted Answer

The answer of All of the following "pairs" are measured...

Question 13

A sonic boom can be heard by a listener

Accepted Answer

A sonic boom is heard when a shock wave passes over a listener, which occurs when an object travels faster than the speed of sound, creating a continuous sonic boom along its path.

Question 14

Some musical (wind) instruments are open at both ends. The length L_bothof the instrument required to achieve a specified fundamental frequency (compared to the length L_oneof a musical instrument closed at only one end) is

Accepted Answer

For a pipe open at both ends, the fundamental frequency corresponds to a wavelength that is twice the length of the pipe. For a pipe closed at one end, the fundamental frequency corresponds to a wavelength that is four times the length of the pipe. Therefore, L_both = 2 L_one.

Question 15

A musical (wind) instrument I_bothis open at both ends. If it has the same fundamental frequency as an instrument I_onethat is closed at one end, the numbers of possible audible harmonics for the two instruments are related by

Accepted Answer

An instrument open at both ends can produce all harmonics (fundamental, second, third, etc.), while an instrument closed at one end produces only odd harmonics (first, third, fifth, etc.), leading to more possible harmonics for the open instrument.

Question 16

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed v_r(< the speed of sound in still air) is roughly the same as if the

Accepted Answer

The Doppler effect describes the change in frequency of a wave in relation to an observer moving relative to the source of the wave. The effect is symmetrical: the observed frequency change when the source moves away from a stationary observer is the same as when the observer moves away from a stationary source at the same speed.

Question 17

A stationary emitter generates a sound of frequency $V$ . The frequency shift $\delta v _ { \gamma }$ if the receiver is moving at a speed that is not < the speed of sound in still air is related to the frequency shift $\delta v _ { e }$ if the emitter moves at precisely the same speed (in the appropriate direction) with respect to a stationary receiver by the relation

Accepted Answer

The answer of A stationary emitter generates a sound of...

Question 18

Confidence in the correctness of the answer for the previous question can be increased by recognizing that

Accepted Answer

Both A and B describe situations that are consistent with the Doppler effect, which is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. A describes a scenario where the frequency increases due to the emitter moving towards the receiver, and B describes a scenario where the frequency decreases due to the receiver moving away from the emitter. Both are correct applications of the Doppler effect principles.

Question 19

The angle $\theta$ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) V_Eby the formula

Accepted Answer

The answer of The angle $\theta$ that the wave front...

Question 20

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r². The assumptions on which this formula depend include all of the following except

Accepted Answer

The formula I ∝ 1/r^2 (where I is the intensity and r is the distance) assumes that the wave energy spreads out uniformly in three-dimensional space (A), the medium through which the wave travels is homogeneous, meaning its properties do not change from one location to another (B), and the medium does not absorb the wave energy (C). Therefore, all the given options are assumptions for the formula, making "none of the above" the correct choice.

Quiz 17: Sound

The intensity of sound when integrated over any Gaussian surface ( ∫IdA\int I d A∫IdA ) that encloses the source yields

The intensity of sound when integrated over any Gaussian surface ( ∫IdA\int I d A∫IdA ) that encloses the source yields

You are in a dark cave; suddenly you hear screeching sounds that are increasing in pitch. From this you discern that something is

If the pitch of the sound is increasing, then the wavelength

For any sound wave traveling in a medium, as the frequency is increased, the following remains constant:

The speed of sound in air v depends on the air pressure p and the air density as

The speed of water waves in deep water depends on the two parameters

The speed of water waves in shallow water depends on the two parameters

Audible sound waves have wavelengths in air on the order of

The speed of sound in air (in meters per second) is on the order of

Diffraction is observed around an obstacle of size ≈\approx≈ 20 λ\lambdaλ . If the obstacle is reduced in size to ≈\approx≈ 2 λ\lambdaλ , the diffraction effect

All of the following "pairs" are measured or expressed in terms of a logarithmic scale except

A sonic boom can be heard by a listener

Some musical (wind) instruments are open at both ends. The length Lboth of the instrument required to achieve a specified fundamental frequency (compared to the length Lone of a musical instrument closed at only one end) is

A musical (wind) instrument Iboth is open at both ends. If it has the same fundamental frequency as an instrument Ione that is closed at one end, the numbers of possible audible harmonics for the two instruments are related by

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed vr (< the speed of sound in still air) is roughly the same as if the

Confidence in the correctness of the answer for the previous question can be increased by recognizing that

The angle θ\thetaθ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) VE by the formula

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r2. The assumptions on which this formula depend include all of the following except

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields

The intensity of sound when integrated over any Gaussian surface ( $\int I d A$ ) that encloses the source yields

Diffraction is observed around an obstacle of size $\approx$ 20 $\lambda$ . If the obstacle is reduced in size to $\approx$ 2 $\lambda$ , the diffraction effect

Some musical (wind) instruments are open at both ends. The length L_bothof the instrument required to achieve a specified fundamental frequency (compared to the length L_oneof a musical instrument closed at only one end) is

A musical (wind) instrument I_bothis open at both ends. If it has the same fundamental frequency as an instrument I_onethat is closed at one end, the numbers of possible audible harmonics for the two instruments are related by

A stationary emitter generates a sound at some particular frequency. The frequency detected by a receiver moving away from the emitter at speed v_r(< the speed of sound in still air) is roughly the same as if the

The angle $\theta$ that the wave front of a Mach cone makes with the direction of travel of a supersonic aircraft is related to the speed of sound v and the speed of the supersonic aircraft (emitter) V_Eby the formula

The intensity I of a wave is related to the distance the wave travels by the expression I ? 18 1/r². The assumptions on which this formula depend include all of the following except