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BOSTON UNIVERSITY

LESSON 6: Resonance

Subject Area

Grade

Estimated Length

Prerequisite knowledge/skills

1. Basic knowledge of the properties of sound

Description of new content

Goals

The purpose of this lab is to verify the equations that express the dependance of length on the resonance frequencies of air columns.

Materials Needed

1. Each student or group should have 1 "Resonance Tube Set, Simple, BASIX". This apparatus can be purchased from the Sargent-Welch catalog for $15.95 each.

2. Each student or group should have access to tuning forks of three different frequencies.

Procedure

Perform the following calculations and fill in the table using the given quantities.
Velocity of sound assumed: 343 m/s

Table 1.

Using the table above as a guide, take the measurements of the resonant lengths of each tuning fork frequency and record data in the table below. Make sure you record your L values in meters.

Table 2.

Using your calculated values and your measured values, determine which of the resonant lengths we are measuring for each frequency, if any. Hint: Compare values of L in Table 2 to values of L1, L2, and L3 in Table 1.

For each of the values of L, determine the percent error and record your values in the following table.

Table 3.

Making the assumption that the majority of the % error could be caused by the actual value of the velocity of sound not being 343 m/s in the room on the day of the experiment, work backwards from the measured value of L and determine the velocity of sound in the room. Hint: Assume that the frequency does not change no matter what the velocity of sound is that day. Record your values in the following table.

Table 4.

Evaluation

Assessment Questions:

Using the graph provided above and your calculations of the velocity of sound find the average and estimate the temperature of the room.
Record your temperature value here: ______________

Use the calculator thermometer to determine the real temperature in the room today and record that value here: _____________

Determine the percent error that exists between the difference in temperature and record that percent error value here: ____________

The error shown by the differences in temperatures represents the majority of the experiment error not associated with changes in the speed of sound. Neatly, on a separate sheet of paper, answer the following questions.

1) What errors were present in the way the measurements were taken in the lab? Describe how these errors might affect the data, specifically.

2) What errors were present in the process of doing the experiment? Describe how these errors might affect the data, specifically.

3) What changes could be made to this experiment to minimize the errors and obtain more accurate values of resonance length?