Situation 16.1
A standing wave of the third overtone is induced in a stopped pipe,1.2 m long.The speed of sound is 340 m/s.
-In Situation 16.1,the number of antinodes in the standing wave pattern is:
A)3
B)4
C)5
D)6
E)7

Question

Quizplus · Accepted Answer

The formula for the frequency of the nth overtone in a closed pipe is:
f = (2n-1) v/4L
where v is the speed of sound and L is the length of the pipe. 
For the third overtone, n=3, so 
f = (2(3)-1) v/4L = 5v/4L
The standing wave in a stopped pipe has nodes at the ends, so there must be an odd number of quarter wavelengths in the pipe. 
If the pipe is 1.2 m long, the quarter wavelength is 0.3 m. Therefore, there must be 4 quarter wavelengths (or 8/4), and thus 4 antinodes. Therefore, the answer is B.

Situation 16.1 a Standing Wave of the Third Overtone Is Induced in Induced