Question

S₁ & S₂ are sources of the sound of frequency 656 Hz. S₁ is moving along OP and S₂ is moving on the circle in an anticlockwise direction with a constant speed of 4√2 m\s. P is a detector that is fixed. Select the correct options (V_sound=300m\s)

• A. When S₂ is at Q, Then frequency it detected by the detector is approximately 647 Hz.
• B. When S₂ is at Q, Then frequency it detected by the detector is 327 Hz.
• C. When S₂ is at R and S1 is coming toward P with a velocity of 4m/s, Then the beat frequency it detected by the detector is 8.86 Hz.
• D. When S₂ is at R and S₁ is coming toward P with a velocity of 4m/s, Then the beat frequency it detected by the detector is 2.56 Hz.

Answer 1

The Correct Option is A, C

The correct options are (A) and (C).



\(f'=\frac{656\times300}{304}\)

\(f'=647.36\,Hz\)

Hence, Option (A) is correct.

From S₂ , \(f'=656\,[\frac{300}{300+4\sqrt2\,cos\,90}]\)

\(f'=656\)

From S₁, \(f''=656\,[\frac{300}{300-4}]\)

\(f''=664.86\)

Beat frequency = \(f''-f'\) = \(664.86-656\) = 8.86 Hz
br>Hence, Option (C) is also correct.