Resonance Column

Materials Required

• Resonance column apparatus
• Tuning forks of known frequency
• Rubber hammer

Real Lab Procedure

• The inner tube of the resonance column is lowered to minimum so that the length of air column inside the tube is very small.
• Take a tuning fork of known frequency and striking 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 are passes down to the 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 that position. This is taken as the first resonant length, l1.
• Then raise the tube approximately about three times the first resonant 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 that position. This is taken as the second resonant length, l2.
• We can now calculate the velocity of sound in air at room temperature by using the relation,

$\nu =2v(l_{2}-l_1)$

• Repeat the experiment with tuning forks of different frequencies and in each time, calculate the value of v.
• The mean of the calculated values will give the velocity of sound in air at room temperature.
• By using the value of v, we can calculate the velocity of sound in air at 00C as,

$v_{0}=v\sqrt{\frac{273}{273+t}}$

Where,  v0 - velocity of sound in air at 00C.

v  - velocity of sound in air at temperature t.

t  - Room temperature.

Simulator Procedure (as performed through the Online Labs)

• Select the surrounding from the drop down list.
• Select the surrounding temperature using the slider.
• Select the diameter of the tube using the slider.
• Select the frequency of the tuning fork using the slider.
• Click on the ‘Hit tuning fork’ button to start/stop vibration.
• Click on the ‘Sound On’ button to hear the sound.
• Drag the inner tube/Change the slider to adjust the height of the air column
• Drag the apparatus to move it down.
• Click on the zoom in icon to view the zoomed area.
• Click on the ‘Show result’ button to see the result.
• To redo the experiment, click on the ‘Reset’ button.

Observations

 No. Frequency of tuning fork, ν (Hz) First resonating length, l1 (cm) Second resonating length, l2 (cm) l2-l1 (×10-2 cm) Velocity, $\small v=2\nu (l_2-l_1)$ (m/s) 1 2 Mean 1 2 Mean 1 2 3 4 5

Calculations

Room temperature, t                                      = ............. 0C

Velocity of sound in air at room temperature, v = ………... m/s

Velocity of sound in air at 00C,

$\small v_{0}=v\sqrt{\frac{273}{273+t}}$

= ............. m/s

Result

Velocity of sound in air at room temperature, v =……....... m/s

Cite this Simulator: