Monthly Archives - April 2011

Making Ripples in Your Lecture Just Got Easier

Every once in a while we come across something that has the chance to make a real difference in the classroom in both engaging the students and making your life as a professor a little easier. We think this may be one of those times. Ripple tanks are such a wonderful way to teach your students about the concepts behind waves, but they can be time consuming to set up and take down. The new Mini Ripple Tank (PA-8638) addresses these issues by providing a completely self contained device, requiring no setup apart from the addition of water. The tank has settings that allow you to adjust the frequency of the wave and light and show everything from perfectly static to rapid wave patterns. It can be used for a small group demonstration, such as a lab, or in combination with the Physics Flex Cam for larger lecture hall settings.Waves are generated in a small, rectangular tank which is placed on a raised, transparent shelf over the internal illumination source. The wave generator is built onto the body of the unit and has an electronic drive circuit to vary the frequency which can also be synchronized to the light source. Dippers can be plugged into the generator by simply pushing them into the stem. A hinged, semi-opaque screen is situated above the tank and images of the wave are projected onto this for study. When access to the tank is required the screen lifts up out of the way. The sides of the tank are designed to absorb waves thus avoiding multiple reflections which cause confused patterns.


The various accessories allow different wave effects to be studied. Strobe illumination gives the best results at all frequencies. Higher frequencies give shorter wavelengths with the waves closer together. Since the patterns are stationary a sheet of tracing paper or OHP film can be placed on the viewing screen and drawings made for subsequent analysis.


Observe the incident and reflected wave directions from plane waves. Vary the plate angle to see the effect. Circular waves and the reflection of these can also be studied.


Plane wave diffract around and behind the plate. If two plates are used with a narrow gap between them, circular waves can be seen.


Use the twin point dipper with nothing else in the tank. Constructive and destructive interference will be seen where the two sets of circular waves meet.


Refraction relies on the different speeds of water waves in different depths of water. As the waves slow down in the shallow water they bend round slightly towards the normal. With a single point dipper, the distortion of the circular wave pattern is very obvious. With a convex lens shape the plane waves create a focusing effect. With a concave shape and plane waves there is a divergence of the waves as they pass over the shape.

Check Out These Cool Tools!

Mini Ripple Tank

Mini Ripple Tank
The Mini Ripple Tank creates Reflected, Diffracted, Refracted, and Interference waves with no fuss! It is compact and easy to use; don’t be afraid to let students experiment in groups and see for themselves.
Learn More


Physics Flex Cam

Physics Flex Cam
The Physics Flex Cam can easily show waves
or whatever you want to a Lecture Hall or large Classroom. You can also capture to upload or stream to the web.
1280 x 960 SXGA resolution.
Learn More




The Original Ripple Tank

Ripple Tank
The Ripple Tank is the original way to demonstrate wave phenomena in the classroom without an an overhead projector.
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Overhead Projector Ripple Tank

Overhead Ripple Tank
The Overhead Projector Ripple Tank is great for teachers
on a budget. Just use your overhead projector with this
tank and wave generator.
Learn More


Duke students find a way to walk on water… Well, not quite.

The students of Duke University filled a pool with a mix of cornstarch and water to create a non-Newtonian fluid known as”oobleck”. When stress is applied to the liquid it exhibits properties of a solid. Watch as they walk, run and jump on this amazing fluid!

As the YouTube video below shows, stopping or even slowing down while on the stuff can lead to a sinking sensation!

Fluids Behaving Strangely

Key Concept: Non-Newtonian fluids are so named because their properties cannot be described in terms of the concepts of classical fluids. Unlike normal Newtonian fluids, these materials possess properties that depend on how gently or strongly they are stirred or pulled. The study of the flow of materials that behave in this unusual manner is known as rheology.

Quicksand is a common example of a non-Newtonian substance that tends to solidify when placed under stress. The harder a person thrashes around to get out, the worse matters become. Ketchup, on the other hand, behaves in the opposite way. The more it’s shaken, the more readily it flows.

Shear Madness

Oobleck Station Reading is FUNdamental Pittsburgh, Junior League Member VolunteersWhen some non-Newtonian fluids experience a sideways force known as shear, they tend to solidify. A mixture of cornstarch and water is such a fluid. Known to many as Oobleck, this strange substance offers students an opportunity to become amateur rheologists. To make Oobleck, students will need 1 cup of cornstarch, 1/2 cup of water and, if desired, food coloring. Instruct them to:

1. Put cornstarch in bowl.

2. Slowly and while stirring (hands are fine) add the water.

3. Add food coloring as desired.

Once your students have made their Oobleck, you may wish for them to try the following experiments.

1. Have them test the Oobleck by hitting it hard, then softly. They should then stir it quickly, then very slowly.

2. After pouring some of the Oobleck on the table, have students push on the puddle with the side of their hand. The Oobleck will become a solid with the application of a force, but will return to its liquid state as soon as the force is removed.

3. Have students attempt to pick up some Oobleck. Once they have it in their hands, ask them to try to keep it in solid form by continually kneading it.

4. Have students play catch with Oobleck. They will notice that as soon as they stop kneading the Oobleck it will return to its liquid state. This is very obvious as it flies through the air and is caught.

For something that is sure to delight your students you may wish to have them…

Shake it Up: Animating Oobleck with Sound Waves

As you have seen, when stress is applied to a mixture of cornstarch and water it exhibits properties of a solid. Especially interesting is the effect produced when the mixture is disturbed at certain frequencies.

To produce effects that have to be witnessed to be believed, you will need a function generator, an amplifier, a subwoofer and a dish or pie tin containing a mixture of cornstarch and water (Oobleck). You may wish to begin with a mixture of two parts cornstarch and one part water.

Support the container containing the Oobleck over the top of the subwoofer. Begin your experimentation with a 50 Hz signal and adjust until fingers of Oobleck begin to rise from the surface of the liquid. Here are some video examples of some incredible phenomena resulting from the acceleration of Oobleck with sound.

Interesting Links: 

Thanks to Chris Chiaverina for contributing to this article

Check Out These New Cool Tools!


See the inner workings of a mini Van De Graff with the

Fun Fly Stick Science KitA full kit with several extra accessories and a manual full of experiments.
Learn More






Shoot big, beautiful, stable smoke rings across the
largest room.

Smoke CanonThe Smoke Ring Cannon’s ability to produce slow smoke rings can easily show how vortex rings form.
Learn More

Engage, Explain, Explore, Expand and Evaluate…