Question
A source and an observer are moving towards each other with a speed equal to $\frac{v}{2}$ where $v$ is the speed of sound. The source is emitting sound of frequency $n$. The frequency heard by the observer will be
✓
Answer
(d)$n' = n\left( {\frac{{v + {v_0}}}{{v - {v_s}}}} \right) = n\,\left( {\frac{{v + v/2}}{{v - v/2}}} \right) = 3n$
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