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Sound — Physics STD 11 Science — Question

Maharashtra BoardEnglish MediumSTD 11 SciencePhysicsSound3 Marks
Question
State the expression for apparent frequency when listener is stationary and source is.(i) moving towards the listener
(ii) moving away from the listener
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Answer

Let,
$n =$ actual frequency of the source.
$n_0 =$ apparent frequency of the source,
$v =$ velocity of sound in air.
$v_s =$ velocity of the source.
$v_l =$ velocity of the listener.i. If source is moving towards observer then apparent frequency is given by,
$n = n _0\left(\frac{v}{v-v_s}\right)$ i.e., apparent frequency increases.
ii. If source is receding away from observer then apparent frequency is given by, $n = n _0\left(\frac{v}{v+v_s}\right)$ i.e., apparent frequency decreases.

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