From: Samuel Robert Reid [mailto:Reids@Colorado.EDU]
Sent: Wednesday, February 06, 2008 11:49 AM
To: Loeblein Patricia J.
Cc: Perkins, Kathy; Adams, Wendy; Paulson, Archie; Reid, Sam
Subject: Re: wave interference one more thing

 

From: Samuel Robert Reid [mailto:Reids@Colorado.EDU]
Sent: Sat 2/2/2008 12:15 PM
To: Loeblein Patricia J.
Cc: Perkins, Kathy; Adams, Wendy; Paulson, Archie; Reid, Sam
Subject: Re: wave interference one more thing

Trish, Kathy, Wendy,

 

 

My comments are below your recommendations below. I'll wait to hear feedback from Kathy and/or Wendy before working on any of this.

1. It would be good if the audio could be linked to the detector like the listener in the Sound sim.

>>Since this simulation allows arbitrary waveforms, and not just sinusoidal, it would be difficult to implement exactly what it would sound like at the listener.  If we just want to assume that sinusoidal waves reach the listener and ignoring doppler effect, and any barriers etc, then this would be tractable, but still difficult.

The main reason I thought about this idea was from a lab I used to do. The students would set up two sources (starting with sound) and then use recievers to find the nodal and antinodal lines. I wonder if there would have to be an experiment feature where the student would set up an experiment and then the source settings didn't change until they restarted. They could move the reciever to pick up only what orginated. I could photocopy the lab and bring it next week if you would like. It was in a popular lab book written in the late 50s that many HS teachers still use.

Not a bad idea. I don't see any conceptual problems with this.

 

This sounds like a good idea but maybe not worth a huge amount of effort. 

2. I discovered, totally by accident, that the faucet moved. Maybe we need to add a Help. I really liked being able to see the waves in both directions. I think it adds a view that is not demonstrated or explained well in texts and addresses a concept that students struggle with. I was disappointed when I couldn't move the speakers and lights.  Also, it was really easy to observe Doppler!

>>It would be easy to add help, and relatively easy to make it easy to move speakers and lights.  Perhaps we omitted this feature before, since we didn't want to have to model the reflections from the surface of the speaker, or parabolic shape of the light.

Also not a bad idea, although I don't know about computational problems. It might look really slow and crappy in the particle view of sound. The other problem is that the waves for sound and light are slowed down. You can easily overtake the wavefront by moving the faucet, but this isn't really physically realistic for sound (you can create a sonic boom, but it might mislead people about how fast you really have to be going. For light, it's impossible to overtake the wavefront I believe. Maybe you could build this in, so you can't move the flashlight faster than the wavefront...but these are starting to put more into a sim that already has a lot in it.)

 

Let’s discuss in the meeting.

3. For my part, I think a light bulb would be a better image than the flashlight because then students won't have to to understand why the wave appears to go through the parabolic reflector part of the light. The speakers appear more transparent and I don't think there will be a problem.

>> It would be relatively easy to replace the flashlight with a bulb image.
Unless you have data that says students have a problem with the flashlight, I wouldn't change it.

On items like this where we’ve interviewed and it’s worked, we better not change it. Sam, can you put the flashlight back (sorry).

4. It would be nice to be able move the dotted line so you could see energy vs position at other spots. I think you would want to have a "save graph" feature like Hydrogen atom and Skate Park, so you could compare more easily. I would like to be able to move the screen too.

>> It would be relatively easy to make this line movable, and to make it so you can save graphs.  It would be relatively difficult to make it so the screen can be moved, since I would have to break the graphic into two parts. Being able to move the dotted line seems the most important to me.
Again, adding more to an already rich sim. Also, the dotted line doubles as the rotation axis - this could take a lot of programming as well (not sure).

 

I just played with this new version and having the dotted like stay in space while rotating is really confusing.  It just disappears in the water screen.  Students already have some trouble with rotation. I think we should think about this carefully before leaving this change.

5. I tried to change the barrier by dragging and was surprised that I was constrained to use the sliders.

>> You can translate the barrier by dragging it.  Do you want to be able to change the slit width by dragging the edge of the slit?  This seems natural, but I'm not sure all users will figure out this feature. I should have said that I expected to be able to change the slit size by dragging.
Probably a good thing to be able to do - I never noticed you couldn't do this.\

Sam, Let’s add this feature.

6. In the Sound sim, the barrier is solid and its angle can be changed. I can see where it would be helpful to have a similar one with water to go along with traditional water tank demos.  I have commented that I wish the shape of the barrier could be varied. Concave and convex reflection surfaces especially.

>>Since this is a lattice-based simulation, it would be pretty easy to add any arbitrary shape.  However, since the lattice cells are rather large (for computational reasons) I am not sure that the result will look good; it may look discrete & pixellated.  But this would be easy to try.
Again, probably too complicated. If you want to have a water tank sim, that's fine (maybe a good idea). This is supposed to focus on interference.

7. It would be cool to have some objects like we use in water wave tank demos to put in the play area. I do too much hand waving during the equipment based demos. A good start would be to be able to put in just one piece of the barrier so students could see how the waves bend around a corner. (Also, in the traditional demos, some of the pieces are less deep than the water, so refraction is apparent.)

>>See notes on 6 above.

Same comment as #6.

 

Let’s add a water wave sim to our potential list of sims.

8. A pulse feature like Sound so the kids can look at one water wave at a time. I guess that doesn't make sense for light, but then I could ask the kids why not.

>>This would be relatively easy. I think this would be a high priority for me.

 

Maybe save for the water wave sim because it does get complicated for light. 

 

Like I said, I'll wait for feedback and priority before starting on this.

Sam Reid

Loeblein Patricia J. wrote: