Q: A radio station broadcasts at a frequency of $$91.9 \times 10^6$ Hz. If the speed of light is 3.00$$ \times $$10^8 m/s$$, what is the wavelength of the radio wave?

$$\lambda = \frac{3.00 \times 10^8$}{91.9 \times 10^6$} = 3.26 m$$

Q: A string of length $$0.628 m $$and mass $$0.208 g is $$under a tension of $$226 N. $$What is the speed of a wave on this string?

$$v = \sqrt{\frac{226}{2.08 \times 10$$^{-4}$$/0.628}} = 826 m/s$$

Q: A periodic wave has a frequency of $$500 Hz $$and a wavelength of $$0.68 m. $$What is the speed of the wave?

$$v = f \lambda = 500 \times 0.68 = 340 m/s$$

Question 1

Which of the following statements best describes the difference between transverse and longitudinal waves?

Accepted Answer

Transverse waves oscillate perpendicular to the direction of propagation, while longitudinal waves oscillate parallel to the direction of propagation.

Question 2

A radio station broadcasts at a frequency of $$91.9 	imes 10^6$ Hz. If the speed of light is 3.00$$ 	imes $$10^8 m/s$$, what is the wavelength of the radio wave?

Accepted Answer

$$\lambda = \frac{3.00 	imes 10^8$}{91.9 	imes 10^6$} = 3.26 m$$

Question 3

Which of the following best explains why S-waves are not detected on the opposite side of the Earth from an earthquake?

Accepted Answer

S-waves cannot travel through liquids, and the Earth's outer core is liquid.

Question 4

A string of length $$0.628 m $$and mass $$0.208 g is $$under a tension of $$226 N. $$What is the speed of a wave on this string?

Accepted Answer

$$v = \sqrt{\frac{226}{2.08 	imes 10$$^{-4}$$/0.628}} = 826 m/s$$

Question 5

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

Accepted Answer

$$v = f \lambda$$

Question 6

A wave is described by $$y = A \sin(0.85t - 6.0x). $$What is the wavelength $$\lambda of $$this wave?

Accepted Answer

$$\lambda = \frac{2\pi}{6.0} = 1.05 m$$

Question 7

If the period $$T of a $$wave is $$0.01 s$$, what is its frequency $$f$$?

Accepted Answer

$$f = \frac{1}{T} = 100 Hz$$

Question 8

Which of the following is a real-world example of a transverse wave?

Accepted Answer

Light wave

Question 9

A wave travels in the positive x-direction and is described by $$y = A \sin(2\pi ft - 2\pi x/\lambda). $$What is the phase angle $$\phi at$$ $$t = 2 s $$and $$x = 1 m$$, if $$f = 0.5 Hz $$and $$\lambda = 2 m$$?

Accepted Answer

$$\phi = 2\pi (0.5)(2) - 2\pi (1/2) = 2\pi - \pi = \pi$$ radians

Question 10

Which property of waves allows scientists to infer that Earth's outer core is liquid?

Accepted Answer

The absence of S-waves in certain regions (S-wave shadow zones)

Question 11

A periodic wave has a frequency of $$500 Hz $$and a wavelength of $$0.68 m. $$What is the speed of the wave?

Accepted Answer

$$v = f \lambda = 500 	imes 0.68 = 340 m/s$$

Question 12

Which of the following best describes the motion of water particles in a surface water wave?

Accepted Answer

They move in circular paths, combining both transverse and longitudinal components.

Question 13

If a string's tension is quadrupled, how does the speed of a wave on the string change?

Accepted Answer

The speed doubles, since $$v = \sqrt{F/\mu}.$$

Question 14

Which of the following is NOT a characteristic of all waves?

Accepted Answer

They carry matter from one place to another.

Question 15

A wave on a string is described by $$y = 0.05 \sin(4\pi t - 2\pi x). $$What is the amplitude of the wave?

Accepted Answer

$$0.05$$ units

Question 16

Which of the following best describes a seismic P-wave?

Accepted Answer

A longitudinal wave that can travel through both solids and liquids.

Question 17

If the mass per unit length of a string is doubled while keeping the tension constant, what happens to the speed of a wave on the string?

Accepted Answer

The speed decreases by a factor of $$\sqrt{2}.$$

Question 18

Which of the following equations describes a wave traveling in the negative x-direction?

Accepted Answer

$$y = A \sin(2\pi ft + 2\pi x/\lambda)$$

Waves & Sound: Fundamental Concepts and Applications- lecture 25

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