VELOCITY OF SOUND IN AIR USING RESONANCE COLUMN
To determine the velocity of sound in air at room temperature using the resonance column.
Resonance tube, three tuning forks of known frequencies, a rubber hammer, one thermometer, plumb line, set squares, water in a beaker.
V → Speed of sound in air (m s-1)
l1 and l2 →The length of the air column for the first and second resonance respectively (m)
v → Frequency of the tuning fork (Hz)
· The inner tube of the resonance column is lowered so that the length of air column inside the tube is very small.
· Take a tuning fork of known frequency and strike it with a rubber hammer. The tuning fork now produces longitudinal waves with a frequency equal to the natural frequency of the tuning fork.
· Place the vibrating tuning fork horizontally above the tube. Sound waves pass down the total tube and reflect back at the water surface.
· Now, raise the tube and the tuning fork until a maximum sound is heard.
· Measure the length of air column at this position. This is taken as the first resonating length, l1
· Then raise the tube approximately about two times the first resonating length. Excite the tuning fork again and place it on the mouth of the tube.
· Change the height of the tube until the maximum sound is heard.
· Measure the length of air column at this position. This is taken as the second resonating length l2
· We can now calculate the velocity of sound in air at room temperature by using the relation. V = 2v(l2 − l1)
· Repeat the experiment with forks of different frequency and calculate the velocity.
· The mean of the calculated values will give the velocity of sound in air at room temperature.
Room temperature, t = ____________ ° C
Velocity sound in air at room temperature, V = 2v(l2 − l1) = ____________ m s-1
Velocity of sound in air at room temperature, (V) = ____________ m s-1