A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 4

Question

A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 425 Hz source? (Take the speed of sound in air as 340 m/s)

Professor PC Thomas Classes · Answer

For a closed pipe, the fundamental frequency $f_1 = v / 4L = 340 / (4 	imes 0.2) = 425$ Hz. Since the source is 425 Hz, it excites the first harmonic (fundamental mode).