An organ pipe with length $l$ is open at both ends. When stationary waves are established in the pipe, notes are heard. The speed of sound in the air column is $v$. What is the lowest (fundamental) frequency of the note produced by the pipe?
- A$\frac{2v}{l}$
- B$\frac{v}{l}$
- C$\frac{v}{2l}$
- D$\frac{v}{4l}$