# MCAT Physics Practice Test 7: Waves and Sound

### Test Information

15 questions

minutes

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1. An opera singer has two precisely identical glasses. The singer produces as pure a tone as possible and shatters the first glass at a frequency of 808 Hz. She then sings a frequency of 838 Hz in the presence of the second glass. The second glass will likely:

• A. shatter after a longer amount of time because the applied frequency is higher.
• B. shatter after a shorter amount of time because the applied frequency is higher.
• C. not shatter because the applied frequency is not equal to the natural frequency of the glass.
• D. not shatter because higher-frequency sounds are associated with more attenuation.

2. A child is practicing the first overtone on his flute. If his brother covers one end of the flute for a brief second, how will the sound change, assuming that the new pitch represents the first overtone in the new setup?

• A. The pitch of the sound will go up.
• B. The pitch of the sound will go down.
• C. The pitch of the sound will not change.
• D. The change in the pitch depends on the starting pitch.

3. Which of the following is necessarily true regarding frequency, angular frequency, and period of a given wave?

• A. The magnitude of the angular frequency is larger than the magnitude of the period.
• B. The product of the frequency and period is equal to the angular frequency.
• C. The magnitude of the angular frequency is larger than the magnitude of the frequency.
• D. The product of the angular frequency and period is 1.

4. Ultrasound machines calculate distance based upon:

• A. intensity of the reflected sound.
• B. travel time of the reflected sound.
• C. angle of incidence of the sound.
• D. the detected frequency of the sound.

5. The period for a certain wave is 34 ms. If there is a Doppler shift that doubles the perceived frequency, which of the following must be true?

I. The detector is moving toward the source at a velocity equal to the speed of sound.

II. The source is moving toward the detector at a velocity equal to half the speed of sound.

III. The perceived period is 17 ms.

IV. The perceived period is 68 ms.

• A. III only
• B. I and IV only
• C. II and III only
• D. I, II, and IV only

6. If the speed of a wave is and its wavelength is 10 cm, what is its period?

• A. 0.01 s
• B. 0.03 s
• C. 0.1 s
• D. 0.3 s

7. What is the angular frequency of the third harmonic in a pipe of length 0.6 m with one closed end? (Note: The speed of the sound is approximately )

• A. 213 radians per second
• B. 425π radians per second
• C. 425 radians per second
• D. 850π radians per second

8. A certain sound level is increased by 20 dB. By what factor does its intensity increase?

• A. 2
• B. 20
• C. 100
• D. log 2

9. In some forms of otosclerosis, the stapedial foot plate, which transmits vibrations from the bones of the middle ear to the fluid within the cochlea, can become fixed in position. This limits the displacement of the stapedial foot plate during vibration. Based on this mechanism, which of the following symptoms would most likely be seen in an individual with otosclerosis?

• A. An increase in the perceived volume of sounds
• B. A decrease in the perceived volume of sounds
• C. An increase in the perceived pitch of sounds
• D. A decrease in the perceived pitch of sounds

10. If two waves are 180° out of phase, what is the amplitude of the resultant wave if the amplitudes of the original waves are 5 cm and 3 cm?

• A. 2 cm
• B. 3 cm
• C. 5 cm
• D. 8 cm

11. A student is measuring sound frequencies from the side of a road while walking east. For which of the following situations could the student determine that the difference between the perceived frequency and the actual emitted frequency is zero?

• A. A plane flying directly above him from east to west
• B. A police car passing the student with its siren on
• C. A person playing piano in a house on the street
• D. A dog barking in a car that moves east

12. In which of the following media does sound travel the fastest?

• A. Vacuum
• B. Air
• C. Water
• D. Glass

13. Shock waves have the greatest impact when the source is traveling:

• A. just below the speed of sound.
• B. exactly at the speed of sound.
• C. just above the speed of sound.
• D. well above the speed of sound.

14. As an officer approaches a student who is studying with his radio playing loudly beside him, he experiences the Doppler effect. Which of the following statements remains true while the officer moves closer to the student?

I. The apparent frequency of the music is increased.

II. The same apparent frequency would be produced if the officer were stationary and the student approached him at the same speed.

III. The apparent velocity of the wave is decreased.

• A. I only
• B. II only
• C. I and III only
• D. I, II, and III

15. Ignoring attenuation, how does the intensity of a sound change as the distance from the source doubles?

• A. It is four times as intense.
• B. It is twice as intense.
• C. It is half as intense.
• D. It is one-quarter as intense.

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