Wave Mechanics Question 1122
Question: Two closed organ pipes, when sounded simultaneously gave 4 beats per sec. If longer pipe has a length of 1m. Then length of shorter pipe will be, (v = 300 m/s)
[Pb. PMT 2002]
Options:
A) 185.5 cm
B) 94.9 cm
C) 90 cm
D) 80 cm
Show Answer
Answer:
Correct Answer: B
Solution:
For first pipe $ n _{1}=\frac{v}{4l _{1}} $ and for second pipe $ n _{2}=\frac{v}{4l _{2}} $ So, number of beats = $ n _{2}-n _{1}=4 $
$ \Rightarrow $ $ 4=\frac{v}{4}( \frac{1}{l _{2}}-\frac{1}{l _{1}} ) $
$ \Rightarrow $ $ 16=300( \frac{1}{l _{2}}-\frac{1}{1} ) $
$ \Rightarrow $ $ l _{2}=94.9 $
$ cm $
BETA
