A source of sound of frequency n is moving towards a stationary observer with a speed S. If the speed of sound in air is V and the frequency heard by the observer is n1, the value of n1/n is

(1) (V + S)/V

(2) V/(V + S)

(3) (VS)/V

(4) V/(VS)

(4) By using ${n}^{\text{'}}=n\frac{v}{v-{v}_{S}}$$\frac{{n}_{1}}{n}=\left(\frac{V}{V-S}\right)$

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