Join the Most Relevant JEE Main 2025 Test Series & get 99+ percentile! Join Now
Search any question & find its solution
Question: Answered & Verified by Expert
A speaker emits a sound wave of frequency $f_{0}$. When it moves towards a stationary observer with speed $u$, the observer measures a frequency $f_{1}$. If the speaker is stationary, and the observer moves towards it with speed $\mathrm{u}$, the measured frequency is $f_{2}$. Then -
PhysicsWaves and SoundKVPYKVPY 2011 (SB/SX)
Options:
  • A $f_{1}=f_{2} < f_{0}$
  • B $f_{1}>f_{2}$
  • C $f_{1} < f_{2}$
  • D $f_{1}=f_{2}>f_{0}$
Solution:
1879 Upvotes Verified Answer
The correct answer is: $f_{1}>f_{2}$


$\mathrm{f}_{1}=\frac{\mathrm{f}_{0}[\mathrm{v}]}{\mathrm{v}-\mathrm{u}}$

$f_{2}=f_{0} \frac{[v+u]}{v}$
$f_{2}-f_{1}=f_{0}\left(\frac{u+v}{v}-\frac{v}{v-u}\right)$
$f_{2}-f_{1}=\frac{-u^{2} f_{0}}{(v)(v-u)}=-v e$
$\therefore f_{1}>f_{2}$

Looking for more such questions to practice?

Download the MARKS App - The ultimate prep app for IIT JEE & NEET with chapter-wise PYQs, revision notes, formula sheets, custom tests & much more.