EXPERIMENT TO DETERMINE SPEED OF SOUND IN FREE AIR
RESONANCE TUBE EXPERIMENT
AIM :To determine speed of sound in free air.
METHOD:Using resonance tube , finding 2 resonance positions with 2 different frequency tuning forks.
APPARATUS: Beaker, thermometer, resonance tube,measuring scale, 2 tuning forks of frequencies ν1=512 and ν2=480 , rubber pad
THEORY: Let l1 and l2 be the lengths of air column for the first and second resonance respectively with a tuning fork of frequency ν .
then, λ=2(l2−l1)
the speed, v=νλ
i.e, v=2ν(l2−l1)
DIAGRAM:
PROCEDURE:
- Set the resonance tube vertically upward on flat horizontal surface and fix it.
- then, fix the reservoir (R) on the top.
- after loosening the pinhock , fill water from the beaker in reservoir and tube.
- by lowering the reservoir fix it at lowest position and tightening the pinhock.
- now use tuning fork in the experiment .
- with the help of rubber pad vibrate the tuning fork by placing just above the end of metallic tube. and hold them in vertical plane .
- loosen pinhock little bit and allow water to fall slowly and stop pinhock wen you listen sound in tube. then again very slowly let water fall till you hear maximum loudness from the tube.
- then mark the position and measure it with scale. and write this in l1′falling.
- now, hold the reservoir on top most position and let the water rise in the tube till you hear sound in tube and then mark point where you hear maximum loudness and write this in l1′rising .
- now increase the water level to thrice that n previous step. and then again follow step 7,8,9 and write reading in l2′ falling and l2′ rising.
- and now repeat steps 7,8,9,10 for the another tuning fork of different frequency. and mark its reading in l1"and l2" .
- note temperature of air column of the resonance tube with the help of thermometer .....at the beginning t1 and at the end t2 .
- note all observation in a table .
OBSERVATION:
Mean temperature in air column :t=2t1+t2=28° (let,room temperature)
frequency of first fork, ν1=512 HZ
frequency of second fork ν2=480 HZ
⟹ Observation table
CONCLUSION
This include calculations and result of the experiment.
From 1st tuning fork ; v1=2ν(l2′−l1′)=35020.8cm/s
From 2nd tuning fork; v2=2ν(l2"−l1")=35136.0cm/s
therefore; Mean velocity at room temprature :
v=2v1+v2=35078cm/s
∴Velocity of sound in air at room temperature is:
=35078cm/s=350.78m/s
PRECAUTIONS:
- Resonance tube should be kept vertically and kept fix on horizontal surface.
- Pinch cock must be in proper condition and be tight .
- forks should be vibrated gently with help of rubber pad.
- tuning fork should be vibrated in vertical plane at end of tube.
- Reading should be noted in table carefully.
- do not use broken scale or set square to measure length.
- all the glass apparatus like tube and beaker should be kept gently and to be hold gently.
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