A stationary source emits sound waves of frequency 500 Hz. 

Two observers moving along a line passing through the source

detect sound to be of frequancies 480 Hz and 530 Hz. Their respective speeds

are in m/s,

(Given speed of sound = 300 m/s)

  • Option 1)

    12,16

  • Option 2)

    12,18

  • Option 3)

    16,14

  • Option 4)

    8,18

 

Answers (1)

 

Frequency of sound when source is stationary and observer is moving towards source. -

\nu {}'= \nu _{0}.\frac{C+V_0}{C }
 

- wherein

C= speed of sound

V_{0}= Speed of observer

\nu _{0}= original frequency

\nu {}'= apparent frequency

 

 

Frequency of sound when source is stationary and observer is moving away from source. -

\nu {}'= \nu _{0}.\frac{C-V_0}{C }

- wherein

C= speed of sound

V_{0}= Speed of observer

\nu _{0}= original frequency

\nu {}'= apparent frequency

 

 

f_A=\frac{(300-V_A)}{300}\times 500=480........................(1)

f_B=\frac{(300+V_B)}{300}\times 500=530........................(2)

From (1)

300-V_A=288

V_A=12 \: \: m/s

From (2)

300+V_B=318

V_B=18 \: \: m/s


Option 1)

12,16

Option 2)

12,18

Option 3)

16,14

Option 4)

8,18

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