SPEED OF SOUND - RESONANCE TUBE

AIM:

The aim of this experiment is to use the resonance of an air column in a tube to find the speed of sound in air.

YOU WILL NEED:

A 1 litre measuring cylinder, a glass, plastic or metal tube with a diameter of about 2.5 cm, a ruler, a set of tuning forks, a retort stand, boss and clamp thermometer, a large rubber bung or a wood block.

WHAT TO DO:

Set up the apparatus as shown. Strike a tuning fork on the rubber bung, NOT THE BENCH and hold it over the end of tube T.

Move the tube up and down until a resonance position is obtained. Measure the length (L) of the tube above the water.

Repeat the procedure with other tuning forks. For each resonance measure the length (L) of the open end of T above the water. For each length L find the wavelength (λ = 4L).

ANALYSIS AND CONCLUSIONS:

Plot a graph of f against 1/L. The gradient of your graph (f/(1/L)) = v/4.
Calculate the velocity of sound (v).
The velocity is related to the fundamental resonant frequency (f) by the equation:

Velocity = 4Lf

An alternative method is to find the second resonance length (L’) for each frequency.

L’ - L = λ/2 = v/2f

This eliminates end corrections.