Name:
Lab Partner(s):
Date lab performed:
Dr. Julie J. Nazareth
Physics 122L/132L
Section:
Resonance of Air Columns
Table 1:
Resonance
(antinode)
positions
x1 (
)
x2 (
)
x3 (
)
x2-x1 (
)
x3-x2 (
)
average diff. in
antinode
positions
Δx (
)
wavelength,
λ(
)
Inverse
frequency of
tuning fork,
1/f (
)
512 Hz
480 Hz
426.7 Hz
384 Hz
341.3 Hz
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Graph: Plot λ vs. 1/f (wavelength versus inverse of frequency) for the five tuning forks. Use
meters (m) for the units of λ and seconds (s) for the units of 1/f. Draw a best fit straight line
and calculate the speed of sound, v, from the slope. Circle or box the points (NOT data points)
used to calculate the slope. You may do this graph as a shared graph (between lab partners) IF
you draw the graph during class and get it signed off by the instructor BEFORE you leave class.
Table 2: Speed of sound results from two different techniques
Room temperature,
Speed of sound in air
Speed of sound in air
Tc (
)
from eqn 3, ve (m/s)
from graph, vg (m/s)
±
±
Table 3: Predicted and actual resonant points for tuning forks at 320 Hz and 288 Hz
f = 320 Hz
f = 288 Hz
wavelength, λ (m) =
wavelength, λ (m) =
Predicted
Predicted
Actual
Predicted
Predicted
Actual
air column position on position on air column position on position on
Number of
length,
inner pipe, inner pipe,
length,
inner pipe, inner pipe,
nodes
L(
)
dp (
) dexp (
) L(
)
dp (
) dexp (
)
n=1
n=2
n=3
n=4
*** Note: Not all air column lengths can be made with this lab’s experimental apparatus. If the
predicted position on the inner pipe is not between 0 and 90 cm , put “N/A” in the table. ***
Lab: Resonance of Air Columns
Updated 4/12/16
Calculations: Show the following calculations in the space provided below or on an attached
sheet of paper. As always, include units in your calculations. Be reasonable with your digits,
but significant digits are not required except for the calculation with uncertainty.
• Speed of sound in air from equation 3 (include uncertainty)
veq3 = 331.4 m/s + (0.6 m/(s °C)) (
±
) =
±
•
Slope of the graph of λ vs. 1/f
•
Wavelength of sound produced by the 288 Hz tuning fork (step 8), using the speed of
sound determined from equation 3 (ignore uncertainty when calculating wavelength).
λ288Hz =
•
Length of the air column for n = 1, 2, 3, 4 (L1, L2, L3, L4) using L = nλ/2 for the 288 Hz
tuning fork
L1 = (1) λ/2 = (1)(
m)/2 =
L2 = (2) λ/2 = (2)(
•
SHOW CALCULATION ON CORNER OF GRAPH
m)/2 =
L3 = (
)(
m)/2 =
L4 = (
)(
m)/2 =
Predicted position on the inner pipe of the apparatus assuming the outer pipe is 90 cm
long, for L1, L2, L3, and L4 for the 288 Hz tuning fork. If the air column cannot be
accommodated with this lab’s experimental apparatus (accommodates air column lengths
between approximately 0.9 and 1.80 m), state so in place of the particular calculation for
that value of n.
For L1: dp1 =
– 0.90 m =
For L2: dp2 =
– 0.90 m =
For L3: dp3 =
– 0.90 m =
For L4: dp4 =
– 0.90 m =
Questions: Answer on an attached sheet of paper.
1. If the room temperature decreases, what happens to the wavelength. Explain why.
Extra Credit question: Another tuning fork in the set has a frequency of 256 Hz. Why wasn’t
this one used during the experiment? Be Specific. You may want to do some calculations like
the ones above to help you answer this question. If you do, please show your calculations/work.
Don’t forget to write your conclusion! (Be sure to compare and discuss the two values you have
found for the speed of sound. If they are not the same within uncertainty, why do you think that
is? How close were your expected resonant points for the 320 Hz and 288 Hz tuning forks to the
actual resonant points you measured in step 9? If your values were not “close,” why do think
that was? Make sure you define what “close” is (e.g., percent difference less than 5% or 25%,
etc.))
Lab: Resonance of Air Columns
Updated 4/12/16