Q: Which equation correctly expresses Snell's Law for sound waves at a boundary between two media?

$$\frac{\sin \theta_i}{\sin \theta_r} = \frac{V_{L1}}{V_{L2}}$$

Question 1

Which of the following best describes the phenomenon of refraction for sound waves?

Accepted Answer

The bending of sound waves due to a change in speed of propagation at a boundary interface.

Question 2

A sound wave travels from air (medium 1) into water (medium 2), where the speed of sound is greater. According to Snell's Law, what happens to the direction of the sound wave?

Accepted Answer

The sound wave bends away from the normal and toward the boundary.

Question 3

Which equation correctly expresses Snell's Law for sound waves at a boundary between two media?

Accepted Answer

$$\frac{\sin 	heta_i}{\sin 	heta_r} = \frac{V_{L1}}{V_{L2}}$$

Question 4

If the speed of sound decreases with altitude due to a temperature decrease, what is the effect on sound propagation?

Accepted Answer

Sound waves are refracted upward, creating an acoustical shadow.

Question 5

Why does thunder sound like a low-frequency rumbling when heard from a distance?

Accepted Answer

High-frequency sound waves are attenuated more quickly than low-frequency waves.

Question 6

Which of the following factors does NOT directly affect the speed of sound in air?

Accepted Answer

The color of the medium.

Question 7

A string of length $$L$$ fixed at both ends supports a standing wave. What is the wavelength of the fundamental mode?

Accepted Answer

$$\lambda = 2L$$

Question 8

For a tube open at one end and closed at the other, which harmonic frequencies are present?

Accepted Answer

Only odd integer multiples of the fundamental frequency.

Question 9

Given a 25 cm tube open at one end, what is the fundamental frequency if the speed of sound is $$340\ \mathrm{m/s}$$?

Accepted Answer

$$340\ \mathrm{Hz}$$

Question 10

Which of the following statements about standing waves is TRUE?

Accepted Answer

Nodes are points of minimum vibration, and antinodes are points of maximum vibration.

Question 11

What is the distance between two successive nodes in a standing wave on a string of length $$L$$ fixed at both ends?

Accepted Answer

$$L/2$$

Question 12

Which of the following best explains why sound attenuation is greater in dry air?

Accepted Answer

Dry air increases the absorption of sound energy, leading to stronger dampening.

Question 13

A tube is open at both ends and has a length $$L. $$What is the frequency of the second harmonic if the speed of sound is $$c$$?

Accepted Answer

$$f_2$$ = \frac{c}{L}$$

Question 14

Which of the following is a consequence of multiple reflections and refractions of sound waves near the ground surface?

Accepted Answer

Favorable sound propagation near the surface over large distances.

Question 15

If the speed of sound in medium 1 is less than in medium 2, what happens to the wavelength as the wave enters medium 2?

Accepted Answer

The wavelength increases.

Question 16

Which of the following is the correct formula for the speed of sound in air as a function of temperature $$T (in$$ $$^ C$$)?

Accepted Answer

$$c = 331.4 + 0.607 \cdot T$$

Question 17

Which of the following is NOT a way that media can interfere with sound transmission?

Accepted Answer

Amplification: sound energy increases as it passes through a medium.

Question 18

What is the relationship between the frequency of the third harmonic ($$f_3) $$and the fundamental frequency ($$f_0) $$for a string fixed at both ends?

Accepted Answer

$$f_3 = 3$$ $$f_0$$

Question 19

Which of the following best describes a node in a standing wave?

Accepted Answer

A point where there is no vibration.

Question 20

A sound wave is traveling upwind, and the speed of sound decreases with altitude. What is the most likely effect?

Accepted Answer

An acoustical shadow forms as sound waves are refracted upward.

Waves, Sound Propagation, and Standing Waves: Refraction, Attenuation, and Resonance

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