A source is moving towards an observer with a speed of 20 ~m / s … - Vidyadip

MCQ

A source is moving towards an observer with a speed of $20 \mathrm{~m} / \mathrm{s}$ and having frequency of $240 \mathrm{~Hz}$. The observer is now moving towards the source with a speed of $20 \mathrm{~m} / \mathrm{s}$. Apparent frequency heard by observer, if velocity of sound is $340 \mathrm{~m} / \mathrm{s}$, is

A
$240 \mathrm{~Hz}$
B
$280 \mathrm{~Hz}$
✓
$270 \mathrm{~Hz}$
D
$360 \mathrm{~Hz}$

✓

Answer

Correct option: C.

$270 \mathrm{~Hz}$

(c) $n^{\prime}=n\left(\frac{v+v_O}{v-v_S}\right)=240\left(\frac{340+20}{340-20}\right)=270 \mathrm{~Hz}$.

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