# Wave Superposition: Interactive On-line Mac and PC

This material was originally created for Starting Point:Introductory Geology
and is replicated here as part of the SERC Pedagogic Service.

Initial Publication Date: August 30, 2006

## Summary

An Interactive JAVA environment to allow one to look at the linear superposition of up to four ocean waves of different amplitudes and periods. Direction of travel (right or left) and the local depth of water can be specified.

Used this activity? Share your experiences and modifications

## Learning Goals

Students learn definitions of wavelength, wave speed, wave amplitude, and wave period. Distance and time are given so speed=wavelength/period can be verified or deduced by students. Waves reflection and standing waves can also be explored.

Understanding the superposition of waves.
• Standing waves from reflection
• Wave groups with or without reflection

## Context for Use

Although this is an oceanography activity it could be used in any course that has some discussion of waves (electromagnetic waves, sound waves, seismic waves, and water waves).

## Description and Teaching Materials

Here is a beginning sample activity that can be used with this Applet. Although the site was intended primarily for wave superposition exploration our example activity has students look at the wave speed versus depth relationship for shallow waves. Teacher Resource (Acrobat (PDF) 159kB May23 03) with answers and Student Questions (Acrobat (PDF) 156kB May23 03) without answers.

The JAVA model and instructions are all provided at Wave Superposition.

Below are a few sample questions from the activity.

Use 3.0 meters for water depth (do) and the corresponding speed Vo as references. For each depth compare the ratio V/Vo to the ratios of depths suggested in the Table below. How does the speed of a wave change with increasing depth? Does it Increase or Decrease with increasing depth?

click to enlarge either image.

Which formula best describes how the wave speed v is related to the depth d?

## Teaching Notes and Tips

Robert Dalrymple provides some suggested activities for this versatile JAVA applet on wave superposition, see Wave Superposition. It runs well on Mac and PC.

## Assessment

Evaluation of the activity in the Teaching Materials section above provide a good assessment of student understanding for that activity.

## References and Resources

The Virtual Physics Laboratory at Northwestern University has several good applets on waves:
• Longitudinal, Transverse and waves of a Mixed Type
• Sound: Propagation of sound waves from a moving source
• Superposition I: The superposition of two simple harmonic waves. This Applet illustrates superposition, and beat frequencies.
• Superposition II: An animated superposition of two simple harmonic waves. This Applet illustrates superposition, beat frequencies, and the distinction between phase and group velocities.
• Wavepackets
• Wave Reflection: Reflection of a longitudinal wave.

This page from Hyper-physics has a wave speed calculator near the bottom of the page with some theory related ocean wave speeds. It is a good companion for the example activity above.

Other Ocean Applet Links from Robert Dalrymple, Center for Applied Coastal Research,University of Delaware, Newark DE 19716,USA