Question

One method for measuring the speed of sound uses standing waves. A cylindrical tube is open at both ends, and one end admits sound from a tuning fork. A movable plunger is inserted into the other end at a distance L from the end of the tube where the tuning fork is. For a fixed frequency, the plunger is moved until the smallest value of L is measured that allows a standing wave to be formed. Suppose that the tuning fork produces a 449-Hz tone, and that the smallest value observed for L is 0.202 m. What is the speed of sound in the gas in the tube?

Answer 1

The open end is antinode for the standing wave in air column, the closed end (plunger) is nod, => L= λ/4 => λ = 4•L.
λ=v/f.
4•L = v/f.
v = 4•L• f =4v0.202•449 =362.8 m/s