...use a tuning fork, adjustable length
closed end resonant tube, thermometer and sound wave equations
to verify the 1/4 wavelength closed tube rule
Purpose: Using a tuning fork, adjustable length tube, thermometer and
sound wave equations from the current chapter you will make the
fork and tube resonate at the same frequency and verify the 1/4
wavelength closed tube rule.
Setup:
tuning fork
wood striker block
cup full of water
10 - 25 cm tube
metric ruler
thermometer
Procedure:
Record the room temperature in Celsius (~20 - 30°C)
Use this temperature to calculate the velocityof sound
Go to 3 different stations and get the fork to sing
with the tube. Strike the fork on the wooden block and
adjust the length of the tube by raising or lowering it in the
water, holding the fork very close to the opening in the manner
illsutrated above. At a specific point you will hear the fork
volume dramatically increase. When the volume is loudest (resonance)
carefully measure the length from the top of the tube to the
surface of the water. Record this distance (d) in meters.
According to the closed tube rule 4 x d =
(the length of the resonating tube is 1/4th the length of the
sound wave). Compute and record this.
With this wavelength & the velocity, compute the frequency
of the fork f1
Look on the fork and record the actual frequency f2
Compute your %error (f1-f2)
x 100% / f2
Data:
Temp: ___°C v = 331.5 + .6C = _____.__ m/s
resonant length (d)
(4d)
f1
= v /
f2
on tuning fork
% error
1st station
._____ meters
__.___ meters
_____._ Hz
_____._ Hz
2nd station
._____ meters
__.___ meters
_____._ Hz
_____._ Hz
3rd station
._____ meters
__.___ meters
_____._ Hz
_____._ Hz
Analysis/Conclusion: Finally, update your website with the details of this lab experience
including a descriptive summary, all data, calculations and %error!
Show the instructor a hard copy of your
data above. This lab web entry will be graded according to this rubric.
(the length of the resonating tube is 1/4th the length of the
sound wave). Compute and record this.