Byju's Answer

Standard XII

Physics

Two Parallel Currents

A car approac...

Question

A car approaching a crossing at a speed of 20 m/s sounds a horn of frequency 628 Hz when 80m from the crossing. The apparent frequency heard by an observer 60m from the crossing on the straight road which crosses the road at right angles is (velocity of sound = 330 m/s)

660 Hz

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680 Hz

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640 Hz

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690 Hz

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Solution

The correct option is C 660 Hz
$f^{'} = (\frac{V - V_{0}}{V - V_{s}}) f$

Where, $V =$ Velocity of sound

$V_{o} =$ Velocity of observer

$V_{s} =$ Velocity of source

$V_{s}$ along OS $= (20) \times c o s θ = 16 m / s$

$f^{'} = (\frac{330}{330 - 16}) 628$ $= 660 H z$

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A car approaching a crossing at a speed of 20 m/s sounds a horn of frequency 628 Hz when 80m from the crossing. The apparent frequency heard by an observer 60m from the crossing on the straight road which crosses the road at right angles is (velocity of sound = 330 m/s)

The correct option is C 660 Hzf′=(V−V0V−Vs)fWhere, V= Velocity of sound Vo= Velocity of observer Vs= Velocity of sourceVs along OS =(20)×cosθ=16 m/sf′=(330330−16)628 =660Hz

The correct option is C 660 Hz
$f^{'} = (\frac{V - V_{0}}{V - V_{s}}) f$

Where, $V =$ Velocity of sound

$V_{o} =$ Velocity of observer

$V_{s} =$ Velocity of source

$V_{s}$ along OS $= (20) \times c o s θ = 16 m / s$

$f^{'} = (\frac{330}{330 - 16}) 628$ $= 660 H z$