# Two cars moving in opposite directions approach each other with speed of 22 m/s and 16.5 m/s respectively. The driver of the first car blows a horn having a frequency 400 Hz. The frequency heard by the driver of the second car is [velocity of sound 340 m/s]: Option 1) 350 Hz Option 2) 361 Hz Option 3) 411 Hz Option 4) 448 Hz

D Divya Saini

As we learnt in

Frequency of sound when source and observer are moving towards each other -

$\nu {}'= \nu _{0}.\frac{C+V_{0}}{C-V_{s}}$

- wherein

$C=$ Speed of sound

$V_{0}=$ Speed of observer

$V_{s}=$ speed of source

$\nu _{0 }=$ Original frequency

$\nu {}'=$ apparent frequency

$f_{app}=f_{o}\left[ \frac{v+v_{o}}{v-v_{s}} \right ]=400 \left[ \frac{340+16.5}{340-22} \right ]$

$\therefore f_{app}=448 Hz$

Option 1)

350 Hz

This option is incorrect.

Option 2)

361 Hz

This option is incorrect.

Option 3)

411 Hz

This option is incorrect.

Option 4)

448 Hz

This option is correct.

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