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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,

                                                                  

  • 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,

                                                                  

                                                                                        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,  (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,                      

                                                              

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

 

Result

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