In a gas-filled tube of length $L$, one end is sealed by a piston, and a stationary sound wave is produced. By shifting the piston, the tube length can be changed. The tube length and the sound frequency are adjusted so that the stationary wave always contains two antinodes and two nodes, as shown. The graph illustrates how the frequency $f$ of the stationary sound wave varies with the tube length $L$. What is the speed of sound in the gas in the tube?
- A$150\ \text{m s}^{-1}$
- B$230\ \text{m s}^{-1}$
- C$300\ \text{m s}^{-1}$
- D$340\ \text{m s}^{-1}$