When a train is approaching the stationary observer, the apparent frequency of the whistle of the train is…

When a train is approaching the stationary observer, the apparent frequency of the whistle of the train is $n_1$ and when the train is moving away from the observer, the apparent frequency is $n_2$. The frequency of the whistle noticed by the observer when he moves with the train is _________ .
  1. $\frac{2 n_1 n_2}{n_1+n_2}$
  2. $\frac{\mathrm{n}_1 \mathrm{n}_2}{\mathrm{n}_1+\mathrm{n}_2}$
  3. $\frac{2 n_1 n_2}{n_1-n_2}$
  4. $\frac{\mathrm{n}_1 \mathrm{n}_2}{\mathrm{n}_1-\mathrm{n}_2}$

Solution

No solution. Refer to answer key.

Asked in: AP EAMCET 2017 (26 Apr Shift 2)

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