A siren emitting sound of frequency 500 Hz is going away from a stationary listener with a speed of 50 ~m / s , the frequency of sound heard directly from the siren is

Correct answer: C. 434.2 Hz Here: Frequency of siren =500 ~Hz The speed of siren v_s=50 ~m / s Using Doppler's principle n^ =(v)/(v+v_s) n or n^ =((330)/(330+50)) × 500 or n^ =(330 × 500)/(380) = 434.2 ~Hz

JIPMER 2004

Exam: JIPMER
Year: 2004
Subject: Physics
Chapter: Waves and Sound

JIPMER 2004 · Physics · Waves and Sound

A siren emitting sound of frequency 500 Hz is going away from a...

A siren emitting sound of frequency 500 Hz is going away from a stationary listener with a speed of

50 \mathrm{~m} / \mathrm{s}

, the frequency of sound heard directly from the siren is

Options

A286.5 Hz
B481 Hz
C434.2 Hz
D580 Hz

Correct answer

C. 434.2 Hz

Step-by-step solution

Here: Frequency of siren

=500 \mathrm{~Hz}

The speed of siren

v_s=50 \mathrm{~m} / \mathrm{s}

Using Doppler's principle

n^{\prime}=\frac{v}{v+v_s} n

\quad n^{\prime}=\left(\frac{330}{330+50}\right) \times 500

\quad n^{\prime}=\frac{330 \times 500}{380} = 434.2 \mathrm{~Hz}

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