【Daily Question】Theoretical Foundation 2020.05.25
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Multiple-choice question: During the propagation of a harmonic wave, the vibration velocities of two points that are separated by λ/2 along the direction of wave propagation must be ( ) (A) of the same magnitude but in opposite directions; (B) of the same magnitude and direction; (C) of different magnitudes but in the same direction; (D) of different magnitudes and in opposite directions. Answer: A. Hint: Extra rewards will be given to those who can explain the solution process; the answer can be found in the response!
This post was last edited by h20090630 on 2020-5-25 at 12:18. A. The vibration velocities of two points that are separated by an odd multiple of half a wavelength along the direction of propagation must be of equal magnitude but in opposite directions； The vibration velocities at two points that are separated by an even multiple of half a wavelength in the direction of propagation must be of the same magnitude and in the same direction.
A. When the distance is half a wavelength, the phase difference in harmonic vibration is half a period; as a result, the magnitudes of the vibration velocities of the particles at these two points are equal while their directions are opposite.