Category Archives: Physics

Pendulum Waves

Back when this video was making its rounds on the interwebs (it periodically resurfaces but its popularity seems to be dying out, perhaps behaving like a damped harmonic oscillator), I did a little project explaining the motions involved.

https://dl.dropboxusercontent.com/u/27794628/pendula5.html

It appears something got wonky with the transparency options but everything else seems to work fine.  If you click and drag on the animations you can rotate them in 3D.  Try adding a bunch of extra pendula if your computer can handle rendering it.

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GaN Photoluminescence

I was looking through some old files and I found some real (boring) physics!  Here’s some lab work that I did a couple years back if you want to see what comes of shining lasers on things in a lab.  This is why I don’t want to do research in solid state/material physics.

https://dl.dropboxusercontent.com/u/27794628/lab3blog.html

https://dl.dropboxusercontent.com/u/27794628/lab4blog.html

I do recall a somewhat interesting story regarding that second paper though…  My professor was a referee as a part of the peer review process for some physics journal, and he was sent several papers on GaN as he was somewhat of an authority on the material.  One of the ones he rejected was due to this very effect that is examined in the lab paper.  The author of the rejected paper didn’t understand the cause of the oscillations and kind of fudged the data in an attempt to say it was consistent with phonon oscillations.  The professor happened to know that these types of oscillations should not occur given the particular experimental setup and this lab was devised in part to show that they were in fact due to internal reflections rather than phonon oscillations.  Okay that wasn’t that interesting.

 

Heat Dissipation in a Ring

 

In an effort to put some physics content on here, I give you heat dissipation in a ring.  It starts off with a non-uniform heat distribution, as indicated by the color gradient on the ring, and eventually the heat dissipates as it goes toward equilibrium.  I made this a while back while studying Fourier series, I believe.

Here’s the animation:

HeatRing3

And the code that generated it:

fourierheat

Looking at that mess of code I realize that the whole thing could just as easily be modeled with the temperature being a sine wave as a function of theta in polar coordinates with decreasing amplitude over time.  There was some reason for the specific way it was formulated here that had to do with Fourier analysis.  There were other scraps of code before this part in the Mathematica file that had finite series approximations. I’ll revisit it at some point and see if the reason was useful at all.