“Ripples in the Water”
Student Learning Objectives:
- Create and observe waves in water
- Measure and compare wavelengths and amplitudes
Materials (per team):1 Large Rectangular Tub
2Marbles
1 Pencil
Your Finger
Water
Introduction:
Water waves look like transverse waves. Water waves have crests and troughs that are created by the circular motion of the water molecules as the wave moves through the water; these crests and troughs can be used to measure the properties of the wave.
Preliminary Questions:
A. Do you think the height from which a marble is dropped will affect the wavelength of your water waves?
B. Do you think the height from which a marble is dropped will affect the amplitude of your water waves?
C. How many wavelengths does the following water wave have?
Procedures:
Your teamand will be dropping marbles into water while reading the directions, observing the behavior of the waves, and recording observations.
1. Read all procedures (2-7) before you begin any experimenting. Then carefully read each step as your team completes this activity. Take turns, alternate, using the materials and making observations.
2. Fill your large rectangular tub half full of water.
3. Hold one marble 1 pencil length distance above the water. While everyone on your team watches, drop the marble into the water. Observe the wavelength and amplitude of the wave created. Describe what you observed after the marble hit the water.
4.Hold one marble 3 pencil lengths above the water. While everyone on your team watches, drop the marble into the water. Observe the wavelength and amplitude of the wave created. How did this wave compare to the first wave? You may want to repeat your drops (from each of the heights) a couple of times to confirm your team observations. Describe the similarities and differences observed by your team as you compared to the waves from the different drops (1 pencil length height versus 3 pencil length height).
5. Have two people hold two marbles 1 pencil length above the water, far enough apart that you will each be able to make your own ripples. While everyone on your team watches, drop the marbles into the water at the same time.
Observe any changes in wavelength and amplitude as the two waves travel through each other. Your team may want to try this 2-3 times, or until yourteam is able to see the changes that occur when the two waves interact. Describe any changes in wavelength and amplitude that occurred when the waves interacted.
6. Use your finger to create waves. Experiment to determine what is required to create a stable wave with the greatest amplitude,using your finger.
- Explain what you need to do to create the highest amplitude water wave.
- How many crests and troughs can you create and maintain in this medium?
- How many wavelengths can you maintain in this medium?
7. Clean Up:
- Pour the water on nearby plants or grass
- Dry everything used in the experiment
- Return all materials to their designated place
Analysis & General Questions:
1) Based on your experiment, what does increased amplitude require? There may be more than one possible answer for this question.
2) Describe what happens to amplitude when two waves interfere, as they travel through each other.
3) Describe the similarities and differences in the patterns created by a marble versus your finger.
Ciardi, TRipples1