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Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15 m/s and 30 m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is (Velocity of sound = 330 m/s).
  • a)
    660 Hz
  • b)
    600 Hz
  • c)
    570 Hz
  • d)
    630 Hz
Correct answer is option 'D'. Can you explain this answer?
Verified Answer
Two trains A and B approach a station from opposite sides, sounding th...
When no beats is listened at the station thus we get the relative frequencies of both the trains are the same.
Hence the relative frequency of the train B is 600 (330/300) = 660
similarly the relative frequency of train A is f(330/315) = 660
Hence we get f = 630Hz
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Most Upvoted Answer
Two trains A and B approach a station from opposite sides, sounding th...
If the stationary observer is hearing no beats then the apparent frequency he is hearing due to source A is equal to the apparent frequency he is hearing due to source B. The direction along the line joining source and observer is taken positive for sign convention. 
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Community Answer
Two trains A and B approach a station from opposite sides, sounding th...
Given:
Velocity of A (VA) = 15 m/s
Velocity of B (VB) = 30 m/s
Real frequency of whistle of B (fB) = 600 Hz
Velocity of sound (vS) = 330 m/s
Observer on platform hears no beats

To find:
Real frequency of whistle of A (fA)

Solution:
1. Let's first calculate the apparent frequency of the whistle of B as heard by the observer on the platform using the formula:

apparent frequency = (velocity of sound ± velocity of observer) / (velocity of sound ± velocity of source) * real frequency

Given that the observer is stationary, the velocity of observer is 0.

For B, the velocity of source is VB = 30 m/s and the sound is approaching the observer, so we use the plus sign for the velocity of sound.

Therefore, the apparent frequency of B as heard by the observer on the platform is:

fB' = (vS + 0) / (vS + VB) * fB
= (330 + 0) / (330 + 30) * 600
= 545.45 Hz (approx)

2. Since the observer hears no beats, the apparent frequency of A as heard by the observer on the platform must also be 545.45 Hz.

For A, the velocity of source is VA = 15 m/s and the sound is moving away from the observer, so we use the minus sign for the velocity of sound.

Therefore, the equation becomes:

fA' = (vS - 0) / (vS - VA) * fA
= 330 / (330 - 15) * fA
= 630 Hz

Hence, the real frequency of the whistle of A is 630 Hz.

Therefore, the correct answer is option D.
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Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15 m/s and 30 m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is (Velocity of sound = 330 m/s).a)660 Hzb)600 Hzc)570 Hzd)630 HzCorrect answer is option 'D'. Can you explain this answer?
Question Description
Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15 m/s and 30 m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is (Velocity of sound = 330 m/s).a)660 Hzb)600 Hzc)570 Hzd)630 HzCorrect answer is option 'D'. Can you explain this answer? for Class 11 2024 is part of Class 11 preparation. The Question and answers have been prepared according to the Class 11 exam syllabus. Information about Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15 m/s and 30 m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is (Velocity of sound = 330 m/s).a)660 Hzb)600 Hzc)570 Hzd)630 HzCorrect answer is option 'D'. Can you explain this answer? covers all topics & solutions for Class 11 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for Two trains A and B approach a station from opposite sides, sounding their whistles. A stationary observer on the platform hears no beats. If the velocities of A and B are 15 m/s and 30 m/s respectively and the real frequency of the whistle of B is 600 Hz, the real frequency of the whistle of A is (Velocity of sound = 330 m/s).a)660 Hzb)600 Hzc)570 Hzd)630 HzCorrect answer is option 'D'. Can you explain this answer?.
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