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Copland CollegeYear 12 - Physics |
| General
Wave Properties - Standing Waves and Resonance:
Click here to go to Java and Flash simulations Answer Sheet - Standing
Waves Last
week you completed two investigations. Formal reports are not required for these, however, you do
need to write up the results in you practical book.
This must be done neatly with appropriate headings.
A very brief description of what you have done is required.
You may cut and paste the experiment sheets to save time.
The main focus will be on the results and what you have found.
Our classroom discussions will help in this regard. The
activities already completed are, Experiments - Second Set: There
are three further experiments that we will be completing this week. Remember
no detailed analysis is required for these activities.
However, you must report your results, complete the
calculations/graphs and write a conclusion. Make
sure that you collect sufficient data and you have a reasonable
understanding of the practical. Remember
for these activities I am able to give you as much assistance as is
necessary. This is unlike the
formal assessment reports that will be given later. 3)
Stationary waves in an air column: This
activity is very similar to the tuning fork resonance tube activity.
The apparatus that we will use allows us to vary the length of the
air column by increasing or decreasing the amount of water in the tube.
Moving the reservoir up and down carries out this adjustment.
The amount of water in the tube can be observed by checking the
attached glass tubing. Work
through the sections of the practical as indicated below. 4)
Stationary waves in an open-ended tube produced by a loud speaker. For
this activity you will have a number of open-ended tubes of various
lengths. The air in these
tubes can be made to resonate by applying a vibrational frequency that is
related to the length of the tubes. Because
the tubes are open ended the first resonance occurs when the length of the
tube is half (1/2) the wavelength of the sound oscillation.
Your task is to measure the tube in metres then calculate the
wavelength of the sound wave that will produce the first harmonic.
Connect the speaker to the oscillator then set the oscillator to
the appropriate frequency. The speed of sound can be taken as 330 m/s.
This allows you to determine the frequency.
Vary the amplitude control to keep any sound to a reasonable value. Hold
the tube over the speaker leaving a space of about 1 cm.
Vary the frequency as necessary to produce the maximum resonance.
The next resonance will occur when the tube is equal in length to
the wavelength and the next when the tube is 1.5 times the wavelength. Calculate the necessary frequencies. Alter the frequency around the calculated value to determine
how this will affect the resonance. Also
examine the relationship between the height of the tube above the speaker
and the resonance that occurs.
5) Stationary waves in
a string produced by an electrically driven oscillator. For this activity follow
the procedures on the sheet Experiment 2 – Standing Waves in a
String. Your task is to compare the velocity of the wave in the string
using two approaches. The
first involves a calculation involving the tension in the string and the
second involves a calculation using the frequency of vibration and the
wavelength. From the
experiment sheet follow through the sections Set-up, Procedure, and
Analysis Method 1. You
will note that an assessment of uncertainty is expected here. The following simulations may help you understand some of the principles involved in these activities. Waves in a String: Click on the following diagram to activate this simulation.
A more complex simulation can be seen below. Here the nature of the standing wave is very easy to observe. Click on the diagram to visit the web site.
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