Wave Mechanics Question 1009
Question: Two sirens situated one kilometer apart are producing sound of frequency 330 Hz. An observer starts moving from one siren to the other with a speed of 2 m/s. If the speed of sound be 330 m/s, what will be the beat frequency heard by the observer
[RPMT 1996; CPMT 2002]
Options:
A) 8
B) 4
C) 6
D) 1
Show Answer
Answer:
Correct Answer: B
Solution:
Observer is moving away from siren 1 and towards the siren 2. Hearing frequency of sound emitted by siren 1 $ n _{1}=n( \frac{v-v _{0}}{v} )=330,( \frac{330-2}{330} )=328Hz $ Hearing frequency of sound emitted by siren 2 $ n _{2}=n,( \frac{v+v _{0}}{v} )=330,( \frac{330+2}{330} )=332Hz $ Hence, beat frequency $ =n _{2}-n _{1}=332-328=4. $
BETA
