To study the physical basis of underwater hearing in frogs, scientists used a vertical tube filled with water to a depth of 1.4 m. A microphone at the bottom of the tube was used to create standing sound waves in the water column. Frogs were lowered to different depths where the standing waves created large or small pressure variations. Because the microphone creates the sound, the bottom of the tube is a pressure antinode; the water’s surface, fixed at atmospheric pressure, is a node.

a. What is the fundamental frequency of this water-filled tube?

b. A frog sits on a platform located 0.28 m from the bottom. What is the lowest frequency that would result in a sound node at this point?