Question 1

Which of the following best describes a mechanical wave?

Accepted Answer

A wave that requires a medium to travel through.

Question 2

A sinusoidal traveling wave is described by $$D(x, t) = A \sin(kx - \omega t + \varphi). $$What does the parameter $$A$$ represent?

Accepted Answer

The amplitude of the wave.

Question 3

The speed of a wave is given by $$v = \lambda f. If $$the wavelength is doubled and the frequency is halved, what happens to the speed?

Accepted Answer

The speed remains the same.

Question 4

For a wave on a string with tension $$T_s$$ and linear density $$\mu$$, the speed is given by $$v = \sqrt{\frac{T_s}{\mu}}. $$What happens to the speed if the tension is quadrupled?

Accepted Answer

The speed is doubled.

Question 5

Sound waves in air are best described as:

Accepted Answer

Mechanical longitudinal waves.

Question 6

The speed of sound in a medium is given by $$v_{sound} = \sqrt{\frac{B}{\rho}}. If $$the density $$\rho$$ increases while $$B$$ remains constant, what happens to the speed?

Accepted Answer

The speed decreases.

Question 7

The intensity $$I of a $$wave is related to its amplitude $$A by$$:

Accepted Answer

$$I \propto A^2$

Question 8

A sound wave has an intensity of $$10^{-10}$$ 	ext{W/m}^2$$. What is its decibel level $$\beta$$?

Accepted Answer

$$\beta = 20 	ext{dB}$$

Question 9

If a source of sound moves toward a stationary observer, which equation gives the observed frequency?

Accepted Answer

$$f = \frac{f_0$}{1 - \frac{v_s}{v}}$$

Question 10

The general wave equation $$\frac{\$$partial^2$$ D}{\partial t^2$} = v^2$ \frac{\$$partial^2$$ D}{\partial x^2$} is $$important because:

Accepted Answer

Its solutions can always be interpreted as traveling waves.

Question 11

A string has a linear density $$\mu = 0.01 	ext{kg/m}$$ and is under a tension $$T_s = 100 	ext{N}. $$What is the speed of a wave on this string?

Accepted Answer

$$v = 100 	ext{m/s}$$

Question 12

If the amplitude of a sound wave is tripled, by what factor does the intensity increase?

Accepted Answer

By a factor of 9.

Question 13

Which of the following is true about the velocity equation $$v(x, t) = -\omega A \cos(kx - \omega t + \varphi)$$?

Accepted Answer

It gives the velocity of a particle at location $$x at $$time $$t in $$the wave.

Question 14

A wave has a frequency of $$500 	ext{Hz}$$ and a wavelength of $$0.6 	ext{m}. $$What is its speed?

Accepted Answer

$$v = 300 	ext{m/s}$$

Question 15

If the bulk modulus $$B of a $$medium is increased while the density $$\rho$$ remains constant, what happens to the speed of sound?

Accepted Answer

The speed increases.

Question 16

The Doppler effect causes the frequency of a sound to:

Accepted Answer

Decrease when the source moves away from the observer.

Question 17

Which equation represents the intensity of a wave?

Accepted Answer

$$I = \frac{P}{a}$$

Question 18

A sound wave has an intensity of $$10^{-8}$$ 	ext{W/m}^2$$. What is its decibel level?

Accepted Answer

$$\beta = 80 	ext{dB}$$

Question 19

If a stationary observer moves toward a stationary sound source, which equation gives the observed frequency?

Accepted Answer

$$f = f_0$ \left(1 + \frac{v_o}{v}\right)$$

Chapter 16: Traveling Waves – Physics Study Notes

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