Final answer:
A 1/2 λ resonator is a closed-end pipe. This is characterized by a standing wave with an antinode at the open end and a node at the closed end, supporting half-wavelength resonance.
Step-by-step explanation:
The type of pipe that is described as a 1/2 λ resonator is a closed-end pipe, also known as a closed-pipe resonator. This is because, as described in the references, a standing wave is formed in the tube with an antinode at the open end and a node at the closed end. In a pipe that is closed at one end and open at the other, the length of the pipe is related to the wavelength of the sound waves produced inside it. A closed-end pipe supports odd-numbered harmonics, and the first overtone is actually the third harmonic of the fundamental frequency. Here, we see that the wavelength (λ') of the first overtone is 4 times the length (L) of the tube divided by 3 (λ' = 4L/3), indicating a closed-end resonator that supports a half-wavelength resonance.