Question:medium
The frequency of sound heard by an observer moving towards a stationary source with certain speed is $n_1$ and if the observer moves away from the same source with same speed, the frequency of sound heard by the observer is $n_2$. If the speed of sound in air is 340ms$^{-1}$ and $n_1 : n_2 = 71:65$, then speed of observer is
The frequency of sound heard by an observer moving towards a stationary source with certain speed is $n_1$ and if the observer moves away from the same source with same speed, the frequency of sound heard by the observer is $n_2$. If the speed of sound in air is 340ms$^{-1}$ and $n_1 : n_2 = 71:65$, then speed of observer is
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The general Doppler effect formula is $n' = n_0 \left(\frac{v \pm v_o}{v \mp v_s}\right)$. Use the top signs for "towards" motion (frequency increases) and the bottom signs for "away" motion (frequency decreases). For ratio problems, this formula simplifies nicely.
Updated On: Mar 30, 2026
- 36 kmph
- 27 kmph
- 15 kmph
- 54 kmph
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The Correct Option is D
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Top Questions on Waves
- Two coherent loudspeakers \(L_1\) and \(L_2\) are placed at a separation of \(10\,\text{m}\) parallel to a wall at a distance of \(40\,\text{m}\) as shown in the figure. On a width \(AB\) on the wall, 10 maxima and minima are found. If the velocity of sound is \(324\,\text{m s}^{-1}\), find the frequency of sound. (Given: \( \sqrt{5}=2.23 \)).
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Two loudspeakers (\(L_1\) and \(L_2\)) are placed with a separation of \(10 \, \text{m}\), as shown in the figure. Both speakers are fed with an audio input signal of the same frequency with constant volume. A voice recorder, initially at point \(A\), at equidistance to both loudspeakers, is moved by \(25 \, \text{m}\) along the line \(AB\) while monitoring the audio signal. The measured signal was found to undergo \(10\) cycles of minima and maxima during the movement. The frequency of the input signal is _____________ Hz.
(Speed of sound in air is \(324 \, \text{m/s}\) and \( \sqrt{5} = 2.23 \))
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