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MHT CET 202624 AprilEvening Shift
Exam
MHT CET
Year
2026
Date
24 April
Shift
Evening Shift
Subject
Physics
Chapter
Waves and Sound

MHT CET 2026 · 24 April · Evening Shift · Physics · Waves and Sound

A source of sound vibrating at frequency 500\ Hz is rotated in a...

A source of sound vibrating at frequency 500 Hz500\ \text{Hz} is rotated in a circle of radius 100π cm\dfrac{100}{\pi}\ \text{cm} at a constant angular speed of 55 revolutions per second. A listener is in the plane of the circle. The maximum and minimum frequency of sound heard are {\{Speed of sound on air =332 m/s}= 332\ \text{m/s}\}

Options

  1. A500 Hz500\ \text{Hz} and 480 Hz480\ \text{Hz}
  2. B516 Hz516\ \text{Hz} and 485 Hz485\ \text{Hz}
  3. C416 Hz416\ \text{Hz} and 490 Hz490\ \text{Hz}
  4. D520 Hz520\ \text{Hz} and 500 Hz500\ \text{Hz}

Correct answer

B. 516 Hz516\ \text{Hz} and 485 Hz485\ \text{Hz}

Step-by-step solution

Given frequency of the source, f0=500 Hzf_0 = 500\ \text{Hz}

Radius of the circular path, R=100π cm=1π mR = \dfrac{100}{\pi}\ \text{cm} = \dfrac{1}{\pi}\ \text{m}

Angular speed, ω=5 rev/s=5×2π rad/s=10π rad/s\omega = 5\ \text{rev/s} = 5 \times 2\pi\ \text{rad/s} = 10\pi\ \text{rad/s}

Linear speed of the source, vs=Rω=(1π)(10π)=10 m/sv_s = R\omega = \left(\dfrac{1}{\pi}\right)(10\pi) = 10\ \text{m/s}

The maximum frequency is heard when the source moves directly towards the listener:

f_\max = f_0 \left( \dfrac{v}{v - v_s} \right)<br><br>f_\max = 500 \left( \dfrac{332}{332 - 10} \right) =500(332322)≈500 \left( \dfrac{332}{322} \right) \approx515.5\ Hz≈\text{Hz} \approx516\ Hz<br><br>Theminimumfrequencyisheardwhen\text{Hz}<br><br>The minimum frequency is heard when the source moves directly away from the listener:

f_\min = f_0 \left( \dfrac{v}{v + v_s} \right)<br><br><br><br>f_\min = 500 \left( \dfrac{332}{332 + 10} \right) = 500 \left( \dfrac{332}{342} \right) \approx 485.3\ \text{Hz} \approx 485\ \text{Hz}<br><br>Answer:<br><br>Answer:516\ \text{Hz} and 485 Hz485\ \text{Hz}
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