Waves - Result Question 77
79. A source and an observer move away from each other, with a velocity of $10 m / s$ with respect to ground. If the observer finds the frequency of sound coming from the source as $1950 Hz$, then original frequency of source is (velocity of sound in air $=340 m / s$ )
(a) $1950 Hz$
(b) $2068 Hz$
(c) $2132 Hz$
(d) $2486 Hz$
[2001]
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Answer:
Correct Answer: 79. (b)
Solution:
- (b) According to Doppler’s effect
$ n^{\prime}=(\frac{v-v_0}{v-v_s}) n=(\frac{340-10}{340+10}) n=\frac{330}{350} \times 1950 $
$ ={ }^{`} 068 Hz $
