AP Physics 1 Question 142: Answer and Explanation

Test Information

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Question: 142

2. Standing waves are produced by a 100-Hz generator in a string of fixed length. The tension in the string is increased until a new set of standing waves is produced. Will the wavelength of the new standing waves be greater than or less than the wavelength of the original standing waves?

  • A. Less, because the tension in the string varies directly with the wave speed, which varies inversely with the wavelength.
  • B. Greater, because the tension in the string varies directly with the wave speed, which varies inversely with the wavelength.
  • C. Greater, because the tension in the string varies directly with the wave speed, which varies directly with the wavelength.
  • D. Less, because the tension in the string varies directly with the wave speed, which varies directly with the wavelength.

Correct Answer: C

Explanation:

C-The speed of waves on a string is given by . All we really need to know is that the bigger the tension, the bigger the wave speed-we know that because tension is in the numerator. Then use v = λf: wavelength is in the numerator, so wave speed varies directly with wavelength.