Q: Which of the following is TRUE about electromagnetic waves?

They can travel through a vacuum at $$c = 3.00 \times 10^8$\ \mathrm{m/s}.$$

Question 1

A mass is attached to a spring and oscillates with simple harmonic motion (SHM). Which of the following statements is TRUE regarding the period $$T$$ and frequency $$f of $$this system?

Accepted Answer

The period and frequency depend only on the mass and the spring constant.

Question 2

A wave travels along a stretched string with tension $$T$$ and linear density $$\mu. $$What is the correct formula for the speed of the wave?

Accepted Answer

$$v = \sqrt{T/\mu}$$

Question 3

Which of the following best describes the difference between mechanical and electromagnetic waves?

Accepted Answer

Mechanical waves require a material medium, while electromagnetic waves can travel through a vacuum.

Question 4

A sound wave travels through air at $$20^\circC $$with a frequency of $$500\ \mathrm{Hz}. $$What is its wavelength?

Accepted Answer

$$0.686\ \mathrm{m}$$

Question 5

A boat is moving to the right at $$5.0\ \mathrm{m/s}$$ relative to the water. An ocean wave is moving to the left with a wavelength of $$110\ \mathrm{m}$$ and a period of $$8.3\ \mathrm{s}. If $$the amplitude is $$1.0\ \mathrm{m}$$, what is the vertical displacement of the boat after $$20\ \mathrm{s}$$, starting from a crest?

Accepted Answer

$$-0.42\ \mathrm{m}$$

Question 6

Which of the following statements about the speed of sound in different media is correct?

Accepted Answer

The speed of sound is fastest in solids, slower in liquids, and slowest in gases.

Question 7

A sinusoidal wave is described by $$y(x, t) = A \cos\left(2\pi\left(\frac{x}{\lambda} - \frac{t}{T}\right)\right). $$What does the parameter $$A$$ represent?

Accepted Answer

The amplitude of the wave.

Question 8

Which of the following is a correct statement about the energy transfer in a wave?

Accepted Answer

A wave transfers energy, but the medium as a whole does not travel.

Question 9

A loudspeaker emits a sound at $$20,000\ \mathrm{Hz} ($$the upper limit of human hearing). What is the wavelength of this sound in air at $$20^\circC$$?

Accepted Answer

$$1.7\ \mathrm{cm}$$

Question 10

Which of the following best describes a transverse wave?

Accepted Answer

The particles of the medium move perpendicular to the direction of wave travel.

Question 11

During an earthquake, S waves and P waves are detected. Which statement is correct regarding their properties?

Accepted Answer

P waves are longitudinal and travel faster than S waves.

Question 12

A physician wants to use ultrasound imaging with a wavelength of $$0.50\ \mathrm{mm} in $$human tissue (speed of sound $$v = 1540\ \mathrm{m/s}). $$What frequency is required?

Accepted Answer

$$3.1\ \mathrm{MHz}$$

Question 13

Which of the following is TRUE about electromagnetic waves?

Accepted Answer

They can travel through a vacuum at $$c = 3.00 	imes 10^8$\ \mathrm{m/s}.$$

Question 14

A snapshot graph of a wave shows the displacement as a function of position at a single instant in time. What does a history graph show?

Accepted Answer

The displacement of one point in the medium as a function of time.

Question 15

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

Accepted Answer

$$v = \lambda f$$

Question 16

A thunderstorm produces a lightning flash, and you hear the thunder $$8.0\ \mathrm{s}$$ later. If the speed of sound in air is $$343\ \mathrm{m/s}$$, how far away did the lightning strike?

Accepted Answer

$$2.7\ \mathrm{km}$$

Question 17

Which of the following is a property of resonance in oscillating systems?

Accepted Answer

Resonance occurs when the driving frequency matches the natural frequency, resulting in large amplitude oscillations.

Question 18

Which of the following best explains why the speed of sound in helium is higher than in air at the same temperature?

Accepted Answer

Helium has a lower molecular mass than air.

Traveling Waves and Sound: Physics for Life Sciences I (Lecture 24, Ch. 15.1-15.4)

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