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MCAT Physics Question — Sound Wave Travel

  • by John
  • Jul 08, 2017
  • MCAT Question of the Day

Why does a sound wave travel through air at a speed of roughly 767mph and through water at a speed of roughly 3300mph?

A. Water is less dense than air.

B. Water has a greater bulk modulus than air.

C. The wave changes phase as it changes medium.

D. Sound is a transverse wave.

Click for Explanation

The speed of sound is proportional to the square root of the bulk modulus and inversely proportional to the square root of the density of the medium. Although the density of water is much greater than air, the bulk modulus of water is also greater than air. Answer choice b) is correct.

A. Water is less dense than air. Incorrect, Water has greater density than air.

B. Water has a greater bulk modulus than air. Correct.

C. The wave changes phase as it changes medium. Incorrect, Although beyond the scope of the MCAT, the phase of a wave refers to a horizontal offset of the waveform that affects neither amplitude nor frequency. A phase change would not affect wave speed.

D. Sound is a transverse wave. Incorrect. Sound is a longitudinal wave, and the type of wave does not affect the speed of propagation.

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