AP Physics 1 Question 260: Answer and Explanation

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Question: 260

6. A sound wave travels through a metal rod with wavelength λ and frequency f. Which of the following best describes the wave when it passes into the surrounding air?

Wavelength    Frequency

  • A. Less than λ    Equal to f
  • B. Less than λ    Less than f
  • C. Greater than λ    Equal to f
  • D. Greater than λ    Less than f

Correct Answer: A



In general, sound travels faster through solids than through gases. Therefore, when the wave enters the air from the metal rod, its speed will decrease. The frequency, however, will not change. Since v = λf must always be satisfied, a decrease in v implies a decrease in λ.