A string fixed at both ends has a length of 1.2 m and a wave speed of 60 m/s. What is the frequency of the third harmonic?
Correct answer: C. 112.5 Hz
- A. 37.5 Hz
- B. 75 Hz
- C. 112.5 Hz
- D. 150 Hz
Explanation
For a string fixed at both ends, nth harmonic frequency fn = (n × v) / (2L). Third harmonic (n=3): f3 = (3 × 60) / (2 × 1.2) = 180 / 1.6 = 112.5 Hz..
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About Waves
Progressive waves transfer energy through oscillations, with wavelength, frequency, amplitude and wave speed related by v = fλ; sound speed depends on the medium. Superposition produces interference and stationary waves in strings and organ pipes, while simple harmonic motion describes the oscillation itself and must be distinguished from wave propagation.
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