Resonance / Speed of Sound

RESONANCE / SPEED OF SOUND

INTRODUCTION

The purpose of this lab is to observe resonation of a sound wave and determine speed of sound. For additional information the student should use the following internet site:

http://pweb.jps.net/~dbaird/phyz/BOP/2.03SHM/L-Fork_It_Over.pdf

EQUIPMENT LIST

1. 3 ft piece of 3” (7.5 cm) or larger pvc pipe sealed on one end to allow for filling with water

2. 3.3 ft piece of 1” (2.5cm) pvc pipe (Must fit inside other pipe)

3. Meter stick for measuring length

4. Tuning fork

5. Thermometer

OBJECTIVES

The student will determine the speed of sound in air.

NEEDED EQUATIONS

l = 4(L + .4d)

Velocity = frequency times lambda v = f l

Velocity = 331.4m/s + [(.6/degree C) times Tc] v = 331.4m/s + (.6Tc)

L = length of column of air at observed resonance point(s).

D = inner diameter of smaller pipe

l = wavelength

Tc = Air Temperature

DETAILED PROCEDURE

1.  Measure the inner diameter of the smaller pipe.

2.  Place smaller pipe inside larger pipe.

3.  Fill larger pipe with water to the reference mark on the inner pipe.

4. / Strike the tuning fork on the heel of your hand or a rubber stopper and place over open end of inner pipe. /

5.  Begin lifting inner pipe until you observe (hear) resonance.

6.  Measure the length (l) of air column from the top of the inner pipe to the water level.

7.  Continue to raise the inner tube to see if the student can observe the second resonance. The student may or may not observe this due to the frequency of the tuning fork.

SAMPLE DATA

Temperature of the air is 25° C. The frequency of the tuning fork is 256 Hz. The inner diameter 0.025m and the length of the column is 0.25m.

Λ = 4(l + .4d)

= 4(.25m + .4(0.25m))

= 1.4m

V = F l

= (256Hz)(1.4m)

= 358.4 measured speed

V = 331.4m/s + .6Tc

= 346.4m/s predicted speed

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