Monthly Archives: May 2013

The Chladni Plate? Mmmm, That Sounds Good.

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Physics demonstrations: Chladni patterns

A metal plate, supported by a post in its center, is vibrated at a single frequency by use of a mechanical driver. For most frequencies, nothing at all happens; when certain special frequencies are hit, however, standing waves appear on the plate, driving the sand away from the points of large vibration to the points of no vibration. By varying the frequency of oscillation, we can find a large number of the so-called resonance frequencies and their accompanying patterns, which become increasingly complex and beautiful as we up the rate of oscillation.

I Wonder if They Called "Bank Shot"

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Scientists Bounce Laser Beams Off Old Soviet Moon Rover

Neat.

One thing that I don’t quite get is this:

a laser beam naturally loses its intensity with distance

If they mean that it spreads out, then it depends on where the beam is focused. Using a beam focused on the moon, (or at twice that distance so the return beam was still converging) would probably be hard, and definitely be an incredibly silly way to do the experiment, since a small beam means you’d have to know precisely where the target was. Using a beam that was expanding (unless you have a laser that has a kilometer-scale beam output) is the right way to do it, so you’re forced by expediency into using an expanding beam with it’s decreasing intensity, but that’s not the same as saying it’s inherent to the laser.

If the claim is something else, then I don’t get it at all.

The Horror, The Horror

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The nightmare of any and every PhD student writing his or her thesis: My laptop was stolen with all my thesis work on it.

I was so paranoid about the lab catching fire and destroying my thesis that I had it on two computers and had about five backup copies. On floppy disks, which was the style of the times, at least one of which was always at home. If the whole science building imploded, I would have a copy that was at most one day’s worth of writing or set of revisions out of date.

Also, having grown up and done high school and college papers in an era before word processors (ask me about my fun with carbon paper!), I am quite aware how much time I saved being able to write my thesis on a computer.