A source of sound having a frequency "f" is moving with the velocity "u" towards a stationary listener. If "v'' is the velocity of the sound, then the apparent frequency of the sound heard by the observer would be:
Correct answer: C. vf/(v-u)
- A. vf / (v + u)
- B. (v +u/v)f
- C. vf/(v-u)
- D. (v - u/v)f
Explanation
Doppler effect formula is= F0 = (v+v0/v +u) f f0= observed frequency v=velocity of sound in air (330m/s) u= velocity of the source v0= velocity of the observer the observer's velocity is zero, so V0 is equal to zero. Substituting this into the Doppler effect equation above, we get the equation of the Doppler effect when a source is moving towards an observer at rest. Now if we rearrange the equation according to our case; Then F0= vf/v-u The sign is negative when the source moves toward the stationary observer and positive when the source moves away from the observer.
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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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