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A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency 1000 Hz normally towards a reflecting wall. The wall approaches the car with a speed of 3.3 m s−1.
  • a)
    The frequency of sound reflected from wall and heard by the driver is 1020 Hz.
  • b)
    The frequency of sound reflected from wall and heard by the driver is 980 Hz.
  • c)
    The percentage increase in frequency of sound after reflection from wall heard by the driver is 2 %.
  • d)
    The percentage decrease in frequency of sound after reflection from wall heard by the driver is 2 %.
Correct answer is option 'A,C'. Can you explain this answer?
Most Upvoted Answer
A driver in a stationary car blows a horn which produces monochromati...
Frequency of Reflected Sound Waves

Explanation:

When a sound wave is reflected from a stationary object, there is no change in its frequency. However, when the object is moving towards or away from the sound source, the frequency of the reflected sound wave changes. This is known as the Doppler effect.

In this problem, the wall is moving towards the car with a speed of 3.3 m/s. Therefore, the frequency of the reflected sound wave will be different from the frequency of the original sound wave.

Part (a):

The frequency of the original sound wave is 1000 Hz. As the wall is approaching the car, the frequency of the reflected sound wave will be higher than the original frequency. The formula for calculating the frequency of the reflected sound wave is given by:

f_r = (v + v_r) / (v - v_s) * f_s

Where,

f_s = frequency of the original sound wave
f_r = frequency of the reflected sound wave
v = speed of sound in air
v_r = speed of the reflecting surface
v_s = speed of the source

Substituting the given values, we get:

f_r = (343 + 3.3) / (343 - 0) * 1000
f_r = 1020 Hz

Therefore, the frequency of the reflected sound wave heard by the driver is 1020 Hz.

Part (c):

The percentage increase in frequency of sound after reflection from the wall heard by the driver can be calculated as:

% increase in frequency = (f_r - f_s) / f_s * 100

Substituting the given values, we get:

% increase in frequency = (1020 - 1000) / 1000 * 100
% increase in frequency = 2%

Therefore, the percentage increase in frequency of sound after reflection from the wall heard by the driver is 2%.

Hence, the correct answers are option A and C.
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Community Answer
A driver in a stationary car blows a horn which produces monochromati...
The frequency received by the wall is
The reflected frequency will be same as the frequency received by the wall. Since the wall is moving towards the driver, the frequency heard by the driver will be,
Now the percentage increase,
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A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency 1000 Hz normally towards a reflecting wall. The wall approaches the car with a speed of 3.3 m s−1.a)The frequency of sound reflected from wall and heard by the driver is 1020 Hz.b)The frequency of sound reflected from wall and heard by the driver is 980 Hz.c)The percentage increase in frequency of sound after reflection from wall heard by the driver is 2 %.d)The percentage decrease in frequency of sound after reflection from wall heard by the driver is 2 %.Correct answer is option 'A,C'. Can you explain this answer?
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A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency 1000 Hz normally towards a reflecting wall. The wall approaches the car with a speed of 3.3 m s−1.a)The frequency of sound reflected from wall and heard by the driver is 1020 Hz.b)The frequency of sound reflected from wall and heard by the driver is 980 Hz.c)The percentage increase in frequency of sound after reflection from wall heard by the driver is 2 %.d)The percentage decrease in frequency of sound after reflection from wall heard by the driver is 2 %.Correct answer is option 'A,C'. Can you explain this answer? for JEE 2024 is part of JEE preparation. The Question and answers have been prepared according to the JEE exam syllabus. Information about A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency 1000 Hz normally towards a reflecting wall. The wall approaches the car with a speed of 3.3 m s−1.a)The frequency of sound reflected from wall and heard by the driver is 1020 Hz.b)The frequency of sound reflected from wall and heard by the driver is 980 Hz.c)The percentage increase in frequency of sound after reflection from wall heard by the driver is 2 %.d)The percentage decrease in frequency of sound after reflection from wall heard by the driver is 2 %.Correct answer is option 'A,C'. Can you explain this answer? covers all topics & solutions for JEE 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A driver in a stationary car blows a horn which produces monochromatic sound waves of frequency 1000 Hz normally towards a reflecting wall. The wall approaches the car with a speed of 3.3 m s−1.a)The frequency of sound reflected from wall and heard by the driver is 1020 Hz.b)The frequency of sound reflected from wall and heard by the driver is 980 Hz.c)The percentage increase in frequency of sound after reflection from wall heard by the driver is 2 %.d)The percentage decrease in frequency of sound after reflection from wall heard by the driver is 2 %.Correct answer is option 'A,C'. Can you explain this answer?.
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