Purpose

To become familiar with mechanical waves properties, including; transverse waves, longitudinal waves, wavelength, frequency, wave speed, and wave behavior.Make sure to go through the Mechanical Wave Introduction PPT before completing this lab.

Problem

all transverse and longitudinal waves have the same properties?

Materials

• extra long slinky
• string
• coil spring

Procedure (Type answers in red to these questions.)

A. Transverse and Longitudinal Waves

1. You and your partner should sit about 2.5 m apart, each with one end of the slinky.
2. Shake one end of the slinky sideways, and watch the pulse travel down the length of the slinky.
3. Starting from the rest position, reach a short distance down the length of the slinky and gather some coils towards you and quickly release them.
4. If you do not have a slinky watch this video to see the two types of waves.https://www.youtube.com/watch?v=iT4KAc0Ag1E
5. Draw the two different types of waves that you created and label the type of wave. Indicate on your diagram how the parts of the slinky move (oscillations) compared to the wave energy transfer. Label one crest, one trough, one compression, and one rarefaction in your diagrams. (1 point for each wave and 1 point for each label for a total of 10 points)

Step 2 drawing

Step 3 drawing

B. Wavelength, Frequency, and Period

• Watch this video which shows these properties.https://www.youtube.com/watch?v=v3CvAW8BDHI .
• Watch this video on some properties of waves:https://www.youtube.com/watch?v=SCtf-z4t9L8
• Here is an explanation of standing frequencies.http://www.physicsclassroom.com/class/sound/Lesson-4/Fundamental-Frequency-and-Harmonics

1. List 3 things that you learned about wave behavior from this slinky demo. (9 points)

• If you do not have a slinky you can use this simulation from PhET (as used in the video)https://phet.colorado.edu/sims/html/wave-on-a-string/latest/wave-on-a-string_en.html

1. Measure how far apart you are and record below.(If you are using the simulation then click on rulers so that you can measure how far apart the 2 ends are.)
2. Shake the slinky to set up the simplest transverse wave possible (one with 2 nodes).(This should look like a jump rope.)
3. Have your partner measure the frequency of this wave by counting the number of times the crest or trough is on one side for a given amount of time, such as 30 seconds. Calculate the period.
4. Use the frequency and the wavelength to calculate the velocity of the wave.(Note: The wavelength of the waves will not be the same as the distance you are apart.)
5. Calculate what frequency you need to make the next simplest standing wave. Try to make it and see how well your results agree.(Reference the link above about standing frequencies and list how you would calculate it here.)
6. Calculate what frequency you need to make a third standing wave. Try to make it and see if your results agree.(Reference the link above about standing frequencies and list how you would calculate it here.)

Distance between ends of the slinky (From step 1): _____________ (1 point)

Table values (15 points)

Wave	Frequency (Hz)	Period (s)	Wavelength (m)	Velocity (m/s)
1
2
3

C. The Speed of the Wave

If you do not have a slinky you may use the PhET simulation from part B.

1. Generate a transverse pulse in the slinky. Time the pulse as it moves the length of the slinky. Record this time.
2. Generate larger and smaller pulses and again time how long they take to reach the other side. Do 5 times and record the time.
3. Do the speeds of the waves vary? (5 points)
4. Experiment to see what you can do to get the waves to move faster and slower. Write conclusion for what makes them move faster and slower on a slinky. (5 points)

Table values (10 points)

Wave	Time (s)
1
2
3
4
5

D. Reflected Waves

1. Have one person hold the slinky firmly while the other person sends a pulse. Record how the phase of the reflected pulse (back to the slinky) compares to the phase of the pulse that was sent. Drawing a diagram may help in your explanation of the wave behavior.
2. Now tie a long piece of string to one end of the spring. Have one person hold the thread while you send a pulse toward the end supported by the string. Observe the phase of the reflected pulse. Record your observations. Drawing a diagram may help in your explanation of the wave behavior.
3. If you do not have a slinky - then watch the end of this video again starting at about 3:55/https://www.youtube.com/watch?v=SCtf-z4t9L8 or use the PhET simulation from part B.

Observations for step 1 (5 points):

Observations for step 2 (5 points):

E. Transmitted Waves

If you do not have a 2 different slinkies you may watch this video to help answer these questions.https://www.youtube.com/watch?v=eLDIJvTEBhg

1. Connect the slinky with the other coil spring. Consider the spring and the slinky as two different media. Stretch the slinky as before.
2. Send pulses down each spring. Observe the behavior at the boundary between the two springs. Observe how a wave changes as it passes from one medium into the other and record your observations below. Again, drawing a diagram may help in your explanation of the wave behavior. (10 points)

F. Interference of Waves

If you do not have a slinky you may rewatch this video to help answer these questions.https://www.youtube.com/watch?v=SCtf-z4t9L8

1. Try several different ways to send pulses from each end of the slinky. Devise an experiment to determine if the waves reflect off each other when they meet or if the pass through each other.
2. Write down the details of your experiment. How did you do it and what conclusion did you reach? (10 points)

Discussion:

1. Use your observations from sections B and C to support the equation v = f. (10 points)
2. How was amplitude affected in the lab? What is the significance of amplitude and how does it relate to the force applied to the slinky?You may find this website helpful https://www.physicsclassroom.com/class/waves/Lesson-2/Energy-Transport-and-the-Amplitude-of-a-Wave in answering this question. (10 points)