IB Waves Lab

Do this lab in groups of three or four preferably. The lot of you can turn in one sheet of paper. For the measurements in feet - one floor tile is a foot.

A: Tension and velocity: (Any open area)

  1. Part 1

    1. While standing, take a small spring and stretch it to a length of 7 feet (1 floor tile is 1 foot) Have your third person stand in the middle to watch the pulses.

    2. Send a pulse down the spring. (Pluck the string like you are playing a bass)

    3. Stretch it to 14 feet

    4. Send a pulse down the spring

  2. Part 2

    1. Click Here to launch the "Wave on a String" PhET

    2. Click the play button to run the PHET

    3. Select "Pulse", "No End", on the top, "Normal" in the middle bottom, and move the slider for damping to "None" and the slider for "Tension" to "High"

    4. Click the green circle on the pulse device, and send a pulse down the string

    5. Move the slider for tension to "Low".

    6. Click the green circle on the pulse device, and send a pulse down the string

  1. Which is faster? (The high tension or the low)


B: Wavelength and frequency (Use the mondo spring in the front of the room)

  1. Part 1

    1. Hold the end right next to the clock

    2. Try wiggling the spring up and down slowly

    3. Try doing it quickly

  2. Part 2:

    1. Click Here to launch the "Wave on a String" PhET

    2. Click the play button to run the PHET

    3. Select "Oscillate", "No End", on the top, "Normal" in the middle bottom, and move the slider for damping to "None" and the slider for "Tension" to the middle. Have your amplitude at 0.75.

    4. Try varying the "Frequency" from 0.70 Hz to 3.00 Hz using the slider at the bottom.

  1. What is the relationship between frequency and wavelength? (As you increase frequency, what happens to the wavelength, as you decrease frequency, what happens)


C: Wavelength and Wavespeed (Use a Chromebook at your desk)

  1. Click Here to launch the "Wave on a String" PhET

  2. Click the play button to run the PHET

  3. Select "Oscillate", "No End", on the top, "Normal" in the middle bottom, and move the slider for damping to "None"

  4. Have your amplitude at 0.75

  5. Try varying the "Tension" from "Low" to "High" using the slider at the bottom. The High tension gives you a high wavespeed, and the Low, a low.

  6. What is the relationship between wavespeed and wavelength?

  7. (As you increase wavespeed (With High tension), what happens to the wavelength, as you decrease wavespeed (With Low Tension), what happens)


D: Reflections (Use a Chromebook, work at your desk)

  1. Click Here to launch the "Wave on a String" PhET

  2. Click the play button to run the PHET

  3. Select "Pulse", "Fixed end", on the top, "Normal" in the middle bottom, and move the slider for damping to "None" and the slider for "Tension" to the middle.

  4. Click the green pulse button to send a pulse down the string. Watch as it reflects off of both fixed ends.

  5. What happens to the pulses as the reflect off the Fixed ends? (Do they reflect upright or inverted?)

  6. Click the "Restart" button at the top, and on the top right click "Loose End"

  7. Click the green pulse button to send a pulse down the string. Watch as it reflects off of the free end on the right.

  8. What happens to the pulses as the reflect off the loose (Free) end? (Do they reflect upright or inverted?)


E: Types of waves (Do this on one of the tables in the room)

  1. Watch this video : https://www.youtube.com/watch?time_continue=7&v=_2HE4AlSE_s (Turn up the volume)

  2. Make those waves with a small slinky. (Stretch it out about 7 feet)

  3. In your own words, write a definition of a longitudinal wave, and a transverse wave

F. Superposition (Do this on the floor in the hall outside the room)

1. Watch this video: https://www.youtube.com/watch?v=ypcX1LdmMPM
2. Watch this video: https://www.youtube.com/watch?v=QjukfQttKAQ

Destructive Interference:

Constructive Interference:


3. Do that with the cups - set them out in the hall 2 feet apart. Stretch a big slinky out 20 feet in the hall.
Send two pulses that constructively interfere, and knock one of the cups to the side, leaving the other
Send two pulses that destructively interfere right where the cups are, leaving them both un-disturbed

G. Standing waves (Any open area for the first one, and with a Chromebook at your desk)

Both ends fixed:

Watch this video: https://www.youtube.com/watch?v=6iKbv_8f5KQ
Do that with a small spring - see if you can get the first three modes of resonance.

1. Go to https://phet.colorado.edu/en/simulations/category/physics/sound-and-waves and click on "Wave on a String"
2. Click the play button to run the PHET|
3. At the top click "Oscillate", "Fixed End", and at the bottom, set the amplitude to 0.16 cm, and the frequency to 0.41 Hz, the damping to "None" and the Tension to "High"
This is the fundamental frequency (fo) of both ends fixed for this string. The standing waves (resonances) follow a pattern of 1fo, 2fo, 3fo ...
4. See what happens when you change the frequency from 0.41 to 0.82 and 1.23 Hz (Hit "Restart" when you change the frequencies)
5. Draw a picture of the first three modes of resonance of both ends fixed

One end fixed:

  1. Watch this video: https://www.youtube.com/watch?v=h7sjZ0ZOkhs

  2. At the top click "Oscillate", "Loose End", and at the bottom, set the amplitude to 0.16 cm, and the frequency to 0.21 Hz, the damping to "None" and the Tension to "High"

  3. Hit "Restart" at the top

  4. This is the fundamental frequency (fo) of one end fixed for this string. The standing waves (resonances) follow a pattern of 1fo, 3fo, 5fo ...

  5. See if you can get those resonances by changing the frequency. (Hit "Restart" every time you make a change)

  6. Draw a picture of the first three modes of resonance of one end fixed

Both ends free:

  1. Watch this video: https://www.youtube.com/watch?v=QotfmiDDzLw

  2. Draw a picture of the first three modes of resonance of both ends free (sorry)