Making Waves
Name ______Date ______Period ______
Objectives:
- Measure the amplitude, speed, wavelength and frequency of a transverse wave.
- Determine the relationship between amplitude and speed of a wave.
- Determine the relationship between wavelength, frequency and speed of a wave.
Pre-lab Question:
1. What do waves carry?
2. Describe the particle motion relative to the direction of a transverse wave.
3. Define the following terms:
-wavelength
- speed
- amplitude
- frequency
Procedure:
- In an area free of obstacles, stretch out a spring to approx. 2.5- 3 meters. Use the tiles on the floor as a guide point. Keep this same distance throughout the lab.
2. With the spring straightened out to the tape (or tile line), grab the spring near one end and pull sideways 20 cm and release. Use your meterstick to measure your distance. Observe what happens. You have made a transverse wave. In what direction does the spring move as the pulse goes by? ______What happens to the wave once it meets the hand at the end? ______Draw the result. ______
3. Lay spring on floor tile line. Measure and record the amplitude of the wave in Table 1. The distance you disturbed the spring is called the amplitude. The amplitude tells how much the spring is displaced.
4. After you have experimented with making pulses, measure the speed of the pulse. You will need to measure the time it takes the pulse to go the length of the spring. Take several measurements and then average the values. Record your data in the 2nd and 3rdrows of Table 1.
5. Measure the speed of the pulses for two other amplitudes, one larger and one smaller than the value used in step 4. Record your results in the Table 1. How does the speed of the pulse depend on the amplitude? ______
6. Now make waves! Swing one end back-and-forth over and over again on the floor. The result is called a periodic wave. Describe the results (appearance) of the periodic wave you have created. ______
Table 1.
Amplitude(cm) (m) / Time for pulse to travel from one end to the other (s) / Average Time (s) / Speed = length of spring
average time
(cm/s) (m/s)
7. The distance from one crest of a wave to the next is called the wavelength. Notice that you can find the wavelength by looking at the points where the spring does not move. The wavelength is twice the distance between these points. Measure the wavelength of your standing wave. Record the wavelength of your standing wave in Table 2.
8. You can also measure the wave frequency. The frequency is the number of times the wave moves up and down each second. Measure the frequency of your standing wave. Hint: Watch the hands of the person shaking the spring. Time a certain number of back-and-forth motions. The frequency is the number of back-and-forth motions of the hand in one second.
-Record the wave frequency in Table 2. The unit of frequency is the hertz (Hz).
9. Make several standing waves by changing the wave frequency. Try to make 3 different standing waves. Measure the wavelength. Measure the frequency. Record the results in Table 2.
Table 2.
Wavelength (λ)(cm/cycle) / Frequency (f)
(cycles/s or Hz) / Speed (v)
v = λf
Post-Lab Questions:
1. Four characteristics of waves are amplitude, wavelength, frequency and speed.
a. For each characteristic, tell how you measured it when you worked with the spring.
b. For each characteristic, give the units you used in your measurement
c. Which wave characteristics are related to each other? Tell how they are related.
2. Suppose you shake a long spring slowly back and forth. Then you shake it rapidly.
a. Describe how the waves change when you shake the slinky more rapidly.
b. What wave properties change?
c. What wave properties do not change?
3a. What are the units of wavelength, frequency and speed?
b. Tell how you find the wave speed from the frequency and the wavelength.
c. Using your answer to part b, show you the units of speed are related to the units of wavelength and frequency.
4. Was the wave you made in this activity a transverse or compressional wave? Explain the difference between a transverse and compressional wave.