Answer to Question #164369 in Optics for Joe

Question

Describe an experiment to determine the speed of sound in free air. Your account should include

          a diagram, procedure, precautions, observations and conclusions.

Answer 1

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 $\nu_1=512$ and $\nu_2=480$ , rubber pad

THEORY: Let $l1$ and $l_2$ be the lengths of air column for the first and second resonance respectively with a tuning fork of frequency $\nu$ .

then, $\lambda=2(l_2-l_1)$

the speed, $v =\nu\lambda$

i.e, $\boxed{v=2\nu(l_2-l_1)}$

DIAGRAM:

PROCEDURE:

1. Set the resonance tube vertically upward on flat horizontal surface and fix it.
2. then, fix the reservoir (R) on the top.
3. after loosening the pinhock , fill water from the beaker in reservoir and tube.
4. by lowering the reservoir fix it at lowest position and tightening the pinhock.
5. now use tuning fork in the experiment .
6. 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 .
7. 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.
8. then mark the position and measure it with scale. and write this in $l_1 ' falling$.
9. 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 $l_1' rising$ .
10. now increase the water level to thrice that n previous step. and then again follow step 7,8,9 and write reading in $l_2'$ falling and $l_2'$ rising.
11. and now repeat steps 7,8,9,10 for the another tuning fork of different frequency. and mark its reading in "l_1"\n\u200b\t\n and" "l_2"" .
12. note temperature of air column of the resonance tube with the help of thermometer .....at the beginning $t_1$ and at the end $t_2$ .
13. note all observation in a table .

OBSERVATION:

Mean temperature in air column :$t={t_1+t_2\over2}=28\degree$ (let,room temperature)

frequency of first fork, $\nu_1=512$ $H_Z$

frequency of second fork $\nu_2=480$ $H_Z$

$\implies$ Observation table

CONCLUSION

This include calculations and result of the experiment.

From 1^st tuning fork ; $v_1=2\nu(l_2'-l_1')=35020.8 cm/s$

From 2^nd tuning fork; "v_2=2\\nu(l_2"-l_1")=35136.0 cm\/s"

therefore; Mean velocity at room temprature :

$v= {v_1+v_2\over2}=35078 cm/s$

$\therefore Velocity$ of sound in air at room temperature is:

$=35078cm/s=350.78 m/s$

PRECAUTIONS:

1. Resonance tube should be kept vertically and kept fix on horizontal surface.
2. Pinch cock must be in proper condition and be tight .
3. forks should be vibrated gently with help of rubber pad.
4. tuning fork should be vibrated in vertical plane at end of tube.
5. Reading should be noted in table carefully.
6. do not use broken scale or set square to measure length.
7. all the glass apparatus like tube and beaker should be kept gently and to be hold gently.