JEE Mains · Physics · STD 11 - Waves and sound
- JEE Mains 2019
- Hard
- Numerical
Two cars \(A\) and \(B\) are moving away from each other in opposite directions. Both the cars are moving with a speed of \(20\, ms^{-1}\) with respect to the ground. If an observer in car \(A\) detects a frequency \(2000\, Hz\) of the sound coming from car \(B\), what is the natural frequency of the sound source of car \(B\) .... \(Hz\) ? (speed of sound in air \(= 340\, ms^{-1}\))
Pick an option to check your answer.
Answer & Solution
Correct Answer
(A) \(2250\)
Step-by-step Solution
Detailed explanation
Doppler effect:
\(f=\left(\frac{v+u_{0}}{v-u_{s}}\right)\left(f_{0}\right)\)
\(2000=\left(\frac{340+(-20)}{340-(-20)}\right)\left(f_{0}\right)\)
\(\mathrm{f}_{\mathrm{o}}=2250 \mathrm{Hz}\)
\(f=\left(\frac{v+u_{0}}{v-u_{s}}\right)\left(f_{0}\right)\)
\(2000=\left(\frac{340+(-20)}{340-(-20)}\right)\left(f_{0}\right)\)
\(\mathrm{f}_{\mathrm{o}}=2250 \mathrm{Hz}\)
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