What defines a quarter wave resonator?

A quarter wave resonator is specifically characterized by having one end closed and the other end open. This configuration allows for the development of standing waves within the tube. The important aspect of a quarter wave resonator is that the wavelength of the fundamental frequency is four times the length of the tube. Because there is a node (point of minimum air movement) at the closed end and an antinode (point of maximum air movement) at the open end, this tube design effectively reinforces certain frequencies while dampening others.

In this context, the other options do not accurately describe a quarter wave resonator. For instance, a tube that is open at both ends would support different resonances and is classified as a half wave resonator, while a hollow chamber with no ending or a linear passage that is wider at one end does not create the necessary conditions for resonating sound waves in the same manner as a quarter wave resonator. Thus, the defining feature of being closed at one end and open at the other is what makes option B the correct choice.