waves – Physics.Teacher.Momma.

When I was in college my E&M professor introduced me to the falstad apps. It was literally this guy who created a bunch of different JAVA sims. E&M is notoriously challenging due to needing to think and reason in three-dimensional space, so we were encouraged to use the apps to help us visualize static fields.

When I started teaching I decided to poke around and see what else Falstad had created. One of his simulations I use year over year is his ripple tank. It’s incredibly powerful and way less cumbersome than setting up the actual water tables (which was just unfeasible being the only physics teacher with 3 preps)

I just finished my intro activity today so I figured I might as well share. You can find the simulations here.

When the app opens it’s pretty simple. A “faucet” wave like the one in the Phet sim is present. You can see the sliders to adjust for damping and frequency. You can move the source where ever you like and can even toggle into 3D view

What’s pretty awesome is the list of “examples” you can select from the drop down menu.

Single slit, double slit, two-sources, refraction, total internal reflection and a whole slew of topics. You also have complete freedom to add to the simulation using the “add” menu bar at the top.

For my students, we start our waves unit in the following way.

First, we watch the slo mo guys film this ginormous 90 foot wave... with ducks…. which is awesome.

There’s a lot of really great phenomena here. From constructive interference, to refraction and lenses (pay attention to the grid image in the column) to the idea that waves transport energy, not matter.

Next, students head to the sim. I provide them directions on this document and the record their observations on this one.

This activity typically takes a class period and a half. For my advanced students they can usually finish in a class period or I can assign the rest for homework.

When students return the following day, I put this graphic organizer up and prompt them to write their own definition of the behavior based on their observations and a diagram to go with it

During the unit I come back to this app quite often.

We discuss how the design of an auditorium is based on nodal lines

I can drag the single source around to demonstrate doppler effect and sonic booms

If there’s a phenomena I want students to be able to observe, pause and manipulate… there’s usually a way to do it.

The pass along activity is one I developed shortly after attending a Kelly OShea workshop. I wanted to combine modeling with the strengths of white board speed dating and board walks. At the time I didn’t have the large whiteboards and for this particular activity I decided a piece of paper would work best.

Students have already done a reading on waves ahead of time (hopefully).

Part I: I ask students to draw in a pictorial representation of what a longitudinal and a transverse wave might look like.

This is inevitably the most common drawing. Students obviously did the reading, but struggle with a pictorial representation

Students are then told to pass along their paper. I predetermine groups randomly for this activity. Three is best, but if I don’t have a factor of 3 then I put the stragglers into groups of 4. It looks like this:

Student 1 -> Student 2 -> Student 3 -> Student 1

Part II: After students have passed along, they are required to look at the work done by their peer and explain, in words, why that person drew what they drew. Much like speed dating, this requires each of the students to get in the minds of their peers, but without the opportunity for their peers to explain.

Students then pass along again.

The third person takes a look at the previous two answers and then has to think of a way to model each wave type with their bodies.

After the three pass alongs, students get into groups, at this point each paper has been touched by the same persons. They discuss their answers and then they have to get up in front of the class and model with their bodies each wave type.

The physical modeling is great in that the kids are up and moving, but it also provides an opportunity to have a discussion about the model. 7th hour we had a discussion about whether or not doing the worm accurately models a wave (nope, the particle is moving across the room). Similarly, I had a few groups move their whole line down the room which brought up the discussion point about what a wave transfers and doesn’t transfer.

Afterwards, we will go out as a whole class and model transverse and longitudinal waves using an 8-step count.

A unique representation of a longitudinal wave I hadn’t seen before

Tag: waves

Waves Intro Activity with Virtual Ripple Tank

Pass Along – Modeling Waves

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