A musical organ produces notes by blowing air into a set of pipes that are open at one end and closed at the other.
What is the lowest frequency of sound produced by a pipe of length 10m?
(the speed of sound in the pipe is 320m/s)
1. 4Hz 2. 8Hz 3. 16Hz 4. 32Hz

what i got was i found the fundamental frequency which is nv/2L=(1X320)/(2X10) which gives 3. 16Hz. But the answer says its 8 Hz which would make the order of the fundamental frequency 1/2.

Question

A musical organ produces notes by blowing air into a set of pipes that are open at one end and closed at the other.
What is the lowest frequency of sound produced by a pipe of length 10m? 
(the speed of sound in the pipe is 320m/s)
1. 4Hz    2. 8Hz    3. 16Hz   4. 32Hz

what i got was i found the fundamental frequency which is nv/2L=(1X320)/(2X10)  which gives 3. 16Hz. But the answer says its 8 Hz which would make the order of the fundamental frequency 1/2.

theeric · Answer

Hi! I had no idea on this stuff, but found it interesting. So I looked at the Wikipedia page, http://en.wikipedia.org/wiki/Fundamental_frequency It seems that dividing by $2L$ is appropriate for the tube only when both ends are opened or both ends are closed. However, if one is open, and the other is closed, it is appropriate to divide by $4L$, instead. This alteration is half your result, and achieves the answer of "2. 8Hz". I wish you luck in your studies! :)