A) 6
B) 3
C) 0
D) 12
Correct Answer: A
Solution :
[a] Frequency of sound heard by the man from approaching train. \[{{n}_{a}}=n\left( \frac{v}{v-{{v}_{s}}} \right)=240\left( \frac{320}{320-4} \right)=243\,Hz\] Frequency of sound heard by the man from receding train \[{{n}_{r}}=n\left( \frac{v}{v+{{v}_{s}}} \right)\] \[=240\left( \frac{320}{320+4} \right)=237\,Hz\] Hence, number of beats heard by man per sec \[={{n}_{a}}-{{n}_{r}}=243-237=6\]You need to login to perform this action.
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