Partner: Lindsay Marston

Experiment 6: The Oscilloscope

February 27, 2015

Lab Section: Friday 0900 – 1200

Theory

The oscilloscope is a tool used to measure the speed of sound. Because the speed of sound changes frequently and quickly, we cannot use a normal digital meter. The oscilloscope is sensitive enough to read the electrical signals given by sound and display the pattern made by that electrical signal.

Procedure

We followed the procedure given in the manual, however we did not calculate the voltage values. Otherwise, no changes were made to this experiment.

Data

The data obtained:

Part A: Period and Frequency

Sweep Rate

Divisions

Period (theo)

Period (exp)

Frequency

% D (period)

Hum

2.00 ms

2.00

4.00ms

4.04ms

247.5Hz

1%

Whistle

0.200ms

3.20

0.640ms

0.640ms

1.56Hz

0%

Note

2.00ms

0.500

1.00ms

1.00ms

1Hz

0%

Tuning Fork 1

Frequency 2 = 480Hz

2.04ms

490Hz

1.9%

Period 1 = 2.08ms

Tuning Fork 2

Frequency 2 = 512Hz

2.00ms

500Hz

2.6%

Period 2 = 1.95ms

For the values given above, we use the following equations or use the following equipment:

1. Sweep rate: given by the oscilloscope

2. Divisions: divisions are the number of boxes displayed on the oscilloscope. Depending on the pattern, we calculate the amount of boxes one cycle covered.

3. Period (theoretical): Our theoretical period is calculated by multiplying the divisions with the sweep rate:

a. (3.2)(.20ms) = 0.64ms

4. Period (experimental): the oscilloscope gives this data, by measuring the cursors.

5. Frequency is given from either the oscilloscope or the tuning forks.

6. Percent discrepancy uses the following:

a. [(Period(exp) – Period(theo))/Period(theo)] x 100

b. [(4.04 – 4.00)/4.00] x 100 = 1%

Part B: Speed of Sound

Sweep rate = 1ms/div

Microphone Distance (cm +/- 0.1)

Time Delay (ms +/- .001)

0.0cm

0ms

10.0cm

0.250ms

20.0cm

0.530ms

30.0cm

0.810ms

40.0cm

1.09ms

50.0cm

1.37ms

60.0cm

1.67ms

70.0cm

1.96ms

80.0cm

2.30ms

90.0cm

2.58ms

100.0cm

2.88ms

Post-Lab Questions

1. What is the speed of sound from your graph? What is the percent