SPH3U1
Lesson 09
Waves and Sound
RESONANCE IN AN AIR COLUMN LAB
LEARNING GOALS
Students will learn to:

predict and measure the resonant lengths of a column of air.
Purpose:
To determine the resonant lengths of an air column for a given frequency of
sound.
Preparing for the Lab:
[must be completed before lab can be done]
You will be given a tuning fork of some frequency, f. To prepare for this lab, you
must calculate the first two lengths of tubing that will allow standing waves to be
created at this frequency (these are called resonant lengths).
a) In the tubes below, draw the standing wave pattern for the first two resonant
lengths – remember, the frequency and wavelength will be the same for both.
L1
L2
b) How much of a wavelength is present in L1? How much of a wavelength is
present in L2?
c) If you knew the speed of sound and the frequency, how could you calculate L 1
and L2? Do a sample calculation, imagining that f = 450 Hz and Temp = 10oC.
Show all your work.
NOTE: You must include these calculations in the Introduction of your lab along
with some background information about resonance in air columns.
SPH3U1
Apparatus:
Lesson 09
Waves and Sound
- adjustable length air column
- tuning fork
- metre stick
Method:
1.
Obtain a tuning fork from the teacher and record the temperature in the room.
With this information, calculate the first two resonant lengths. The full calculation,
including the diagrams, must be included in the Introduction section of your lab
report.
2.
Set up the apparatus as instructed. Adjust the water level until it is close to your
predicted L1. Sound the tuning fork and hold it above the opening of the cylinder.
DO NOT LET THE TUNING FORK TOUCH THE GLASS AS IT MIGHT BREAK.
3.
While the fork is sounding, slowly lower the reservoir until the sound of the note
gets louder. Adjust the water level in the glass tube using the reservoir until the
loudest resonance is heard. Measure the length of the air column L1.
4.
Repeat the procedure, for L2.
5.
Determine the percent deviation for your results for each length. Show one sample
calculation in the Results & Analysis Section of your report.
Observations:
Table 1: Complete a Title for this Table!!
Predicted (Theoretical) Length (m)
Experimental Length (m)
% Deviation
L1
L2
Error Analysis
Be sure to discuss at least two sources of error and explain how important each one
was (see the lab manual for more detail).
Discussion (write in paragraph form, not numbered answers)
1. If you had a tuning fork of a higher frequency, would your lengths have been longer or
shorter? Explain.
2. Do you believe that this experiment verified the theory of sound waves you have been
learning? Explain.
3. State your conclusion clearly. For example, “It was found that the first two resonant
lengths for a ___Hz tuning fork were ____________ and _____________. These
values deviated from the theoretical lengths by _____% and _____% respectively.”
Complete a Formal Lab Report.