Wave Motion 4 Question 15
14. A whistle giving out $450 Hz$ approaches a stationary observer at a speed of $33 m / s$. The frequency heard by the observer (in Hz) is (Speed of sound $=330 m / s)$
$(1997,1 M)$
(a) 409
(b) 429
(c) 517
(d) 500
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Answer:
Correct Answer: 14. (d)
Solution:
- Source is moving towards the observer
$$ \begin{aligned} f^{\prime} & =f\left(\frac{v}{v-v _s}\right)=450\left(\frac{330}{330-33}\right) \\ f^{\prime} & =500 Hz \end{aligned} $$
