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A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]
- a)396 Hz
- b)363 Hz
- c)374 Hz
- d)385 Hz
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
A whistle of frequen cy 385 Hz rotates in a horizontal circle of radiu...
Velocity of source
vs = rω = 0.50 x 20 = 10 ms-1
Most Upvoted Answer
A whistle of frequen cy 385 Hz rotates in a horizontal circle of radiu...
Understanding the Doppler Effect
The scenario involves a rotating whistle emitting sound waves, and we need to determine the lowest frequency heard by a stationary listener due to the Doppler effect.
Key Parameters
- Frequency of the whistle (f): 385 Hz
- Angular speed (ω): 20 rad/s
- Radius of the circle (r): 50 cm = 0.5 m
- Velocity of sound (v): 340 m/s
Calculating the Linear Velocity
The linear velocity (v_t) of the whistle can be calculated using the formula:
- v_t = r × ω = 0.5 m × 20 rad/s = 10 m/s
Identifying the Frequencies
As the whistle rotates, the frequency perceived by the listener varies depending on whether the whistle is moving towards or away from the listener.
- When moving towards the listener:
- f' = f × (v + v_t) / v
- f' = 385 Hz × (340 m/s + 10 m/s) / 340 m/s
- f' = 385 Hz × (350/340)
- When moving away from the listener:
- f' = f × (v - v_t) / v
- f' = 385 Hz × (340 m/s - 10 m/s) / 340 m/s
- f' = 385 Hz × (330/340)
Calculating the Lowest Frequency
To find the lowest frequency heard by the listener, we need the frequency when the whistle is moving away:
- f' = 385 Hz × (330/340) ≈ 374 Hz
Conclusion
Thus, the lowest frequency heard by the listener, when the whistle is moving away, is approximately 374 Hz, confirming that the correct answer is option 'C'.
The scenario involves a rotating whistle emitting sound waves, and we need to determine the lowest frequency heard by a stationary listener due to the Doppler effect.
Key Parameters
- Frequency of the whistle (f): 385 Hz
- Angular speed (ω): 20 rad/s
- Radius of the circle (r): 50 cm = 0.5 m
- Velocity of sound (v): 340 m/s
Calculating the Linear Velocity
The linear velocity (v_t) of the whistle can be calculated using the formula:
- v_t = r × ω = 0.5 m × 20 rad/s = 10 m/s
Identifying the Frequencies
As the whistle rotates, the frequency perceived by the listener varies depending on whether the whistle is moving towards or away from the listener.
- When moving towards the listener:
- f' = f × (v + v_t) / v
- f' = 385 Hz × (340 m/s + 10 m/s) / 340 m/s
- f' = 385 Hz × (350/340)
- When moving away from the listener:
- f' = f × (v - v_t) / v
- f' = 385 Hz × (340 m/s - 10 m/s) / 340 m/s
- f' = 385 Hz × (330/340)
Calculating the Lowest Frequency
To find the lowest frequency heard by the listener, we need the frequency when the whistle is moving away:
- f' = 385 Hz × (330/340) ≈ 374 Hz
Conclusion
Thus, the lowest frequency heard by the listener, when the whistle is moving away, is approximately 374 Hz, confirming that the correct answer is option 'C'.
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Question Description
A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer? for NEET 2026 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer?.
A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer? for NEET 2026 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2026 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A whistle of frequen cy 385 Hz rotates in a horizontal circle of radius 50 cm at an angular speed of 20 radians s–1. The lowest frequency heard by a listener a long distance away at rest with respect to the centre of the circle, given velocity of sound equal to 340 ms–1, is [2002]a)396 Hzb)363 Hzc)374 Hzd)385 HzCorrect answer is option 'C'. Can you explain this answer?.
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