Question 1

Which of the following best describes the difference between constructive and destructive interference of waves?

Accepted Answer

Constructive interference occurs when two waves meet in phase, resulting in increased amplitude, while destructive interference occurs when two waves meet out of phase, resulting in decreased amplitude.

Question 2

A string fixed at both ends vibrates in its second harmonic. If the length of the string is $$L$$ and the wave speed is $$v$$, what is the frequency of the second harmonic?

Accepted Answer

$$f = \dfrac{2v}{L}$$

Question 3

Which of the following statements about standing waves is correct?

Accepted Answer

Standing waves are formed by the superposition of two waves traveling in opposite directions with the same frequency and amplitude.

Question 4

A sound wave travels through air and then enters water. Which of the following changes as the wave enters the water?

Accepted Answer

The speed of the wave increases, but the frequency remains the same.

Question 5

Which equation correctly relates the speed $$v$$, frequency $$f$$, and wavelength $$\lambda of a $$wave?

Accepted Answer

$$v = f \lambda$$

Question 6

A pipe open at both ends has a length $$L. $$What is the wavelength of the fundamental mode?

Accepted Answer

$$\lambda = 2L$$

Question 7

Which of the following best explains why the pitch of a sound appears higher as a source approaches an observer?

Accepted Answer

The observed frequency increases due to the Doppler effect.

Question 8

Which of the following is the correct formula for the intensity $$I of a $$sound wave at a distance $$r$$ from a point source emitting power $$P$$?

Accepted Answer

$$I = \dfrac{P}{4 \pi r^2$}$$

Question 9

A sound wave has a pressure amplitude $$\Delta p$$ and travels through a medium with density $$\rho$$ and speed $$v. $$What is the intensity $$I of $$the wave?

Accepted Answer

$$I = \dfrac{(\Delta p)^2$}{2 \rho v}$$

Question 10

Which of the following best describes the Bernoulli effect as it relates to sound waves in the ear canal?

Accepted Answer

A pressure difference is created by the movement of air, which helps transmit sound to the inner ear.

Question 11

Which of the following is true about the decibel scale?

Accepted Answer

It is a logarithmic scale used to measure sound intensity.

Question 12

Which of the following best describes the effect of a phase shift of $$\pi$$ radians between two waves of the same frequency?

Accepted Answer

The waves will interfere destructively, resulting in minimum amplitude.

Question 13

Which of the following statements about electric charge is correct?

Accepted Answer

Like charges repel and opposite charges attract.

Question 14

Which law describes the force between two point electric charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

Coulomb's Law: $$F = k_e \dfrac{|q_1$ q_2$|}{r^2$}$$

Question 15

Which of the following is NOT a method by which an object can become electrically charged?

Accepted Answer

By changing its temperature.

Question 16

A neutral metal sphere is brought near a negatively charged rod. What happens to the charges in the sphere?

Accepted Answer

Electrons in the sphere are repelled, causing the near side to become positively charged.

Question 17

Which of the following best describes the direction of the electric field produced by a positive point charge?

Accepted Answer

Radially outward from the charge.

Question 18

Which of the following is a correct statement about nodes in standing waves?

Accepted Answer

Nodes are points where the displacement is always zero.

Question 19

Which of the following best describes the relationship between sound intensity and distance from a point source?

Accepted Answer

Intensity decreases with the square of the distance.

Question 20

Which of the following is a correct statement about harmonics in a string fixed at both ends?

Accepted Answer

The $$nth $$harmonic has $$n$$ antinodes and $$n+1$$ nodes.

Key Concepts for Exam 1: Waves, Sound, and Electrostatics

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