Tag: physics

Optical Discs

Posted on by Brian Garthwaite
Stack of DVD-R discs.
Never used, never to be used.

It really wasn’t that long ago that computers came equipped with optical disc drives, and they were effective means of data storage, and the density you could store on a DVD instead of a CD was pretty exciting. Now? They’re not only borderline-useless, but the features that we used to reference as a cultural touchstone are no longer obvious to our students.

It’s not that they don’t know what these are. It’s that they haven’t handled a million of them to know their dimensions, to understand the diffraction rainbow they make. The physicists around here remember using the inescapable AOL discs as cheap, readily available diffraction gratings back in grad school. The astronomers use their proportions to illustrate the shape of the Milky Way Galaxy. Students now need to physically hold one of these to get the idea, because they don’t have a mental image ready to go.

Our Galaxy, if you were wondering, is roughly proportioned as a CD, only instead of being a millimeter and a half thick, is more like 1,000 light years. Very roughly, anyway.

More Sodium

Posted on by Brian Garthwaite
You’d think it would be more complicated inside.

Here, our more modern sodium light sources, using a clever design that enabled a reduction from the minimum 35W to as little as 18W in 1977. Cool, yeah?

Unfortunately, Philips finally bowed out of the low pressure sodium lamp game in 2019, mean we’ve got these dinosaurs running for as long as we can scour spare lamps online. Once the supply’s gone, it’s gone.

Pure sodium!

Hey, look! Sodium metal! Highly reactive, so it’s inside with a mixture of 99% neon and 1% argon, neither of which deigns to react with, well, anything. That’s why, when it starts up, we see a purplish glow from the noble gases before tube reaches 260°C and vaporizes the sodium. After that, it’s an intense monochromatic yellow-orange that’s hard to look at.

Low Pressure Sodium

Posted on by Brian Garthwaite
Burnt-out low pressure sodium lamp
Toast.

Remember the old, aggressively-yellow street lighting that pre-dated LEDs, ceramic metal halide, and high pressure sodium? Turns out it’s very useful for physics, as the two strong emission lines near 589nm are handy for various experiments.

The lamps themselves are fairly tough, and the ballasts that operate them even more so. But, eventually, they burn out.

General Electric ceased production on these lamps back in 1972. So, no, sorry, replacements are not readily available.

Stamped

Posted on by Brian Garthwaite
Lead brick, painted yellow, stamped by Nuclear Associates of Carle Place, NY.
It’s big, heavy, and boldly colored.

Lead bricks are useful things. This one – still bearing the stamp of Nuclear Associates, of Carle Place, NY – has had its fair share of scuffs and dents. (Lead’s soft stuff, you know.) These days it functions as a handy doorstop and a hands-on tool for explaining the density of matter.

Denser than water, than aluminum, than a nickel-iron meteorite. (All easy samples to acquire for demonstration.) Less dense than osmium; about half as much. (Not on hand, unfortunately.) Definitely less dense than the core of our Sun, by an order of magnitude-plus.

Also no handy samples of stellar core plasma on hand.

Bespoke Breadboard

Posted on by Brian Garthwaite
Long piece of aluminum, in process of machining mounting holes.
So many.

Need a thing, but can’t get it in the right size, right shape, right odd set of dimensions? That’s one reason to keep a workshop in the basement. If we can possibly make it, we’ll certainly try.

Pictured: a custom optics breadboard, for a very specific apparatus, with many, many drilled, tapped, and cleaned 1/4″-20 mounting holes. It’s big, and shiny, and has a bright future ahead!

Probably with lasers or something. Lots of lasers around here.

VHS

Posted on by Brian Garthwaite
Video Home System

Look, sometimes the very specific version you want only exists in a format that’s hard to make use of, like a VHS cassette. That’s why we have helpful, talented people with specific sorts of tech savvy to help us out with bringing oldies but goodies into a more modern format that’s still destined to veer into obsolescence after a while. Thanks, Wes!

For those wondering, AAPT stands for the American Association of Physics Teachers.

In this case, anyway. But for a thought experiment, imagine the collapse of Galloping Gertie as narrated by these other AAPT organizations and/or acronym users:

  • Association of Asphalt Paving Technologists
  • American Association of Psychiatric Technicians
  • American Association of Philosophy Teachers
  • American Academy of Physical Therapy
  • American Academy of Personal Training
  • American Association of Pharmacy Technicians
  • Android Asset Packaging Tool (AAPT2 build tool)
  • International Institute for Animal Assisted Play Therapy
  • AAPT Limited (Australian telecommunications company)
  • ACTTION-APS Pain Taxonomy from the American Pain Society
  • Association of Anatomical Pathology Technology
  • All American Pet Company, Inc. (stock ticker symbol)
  • Alabama Association for Play Therapy
  • Advanced Algebra & Functions Placement Test

Some of those could be really entertaining. Just don’t mention poor Tubby the cocker spaniel to the animal assisted play folks.

Metersticks

Posted on by Brian Garthwaite
Three metersticks
Various vintages.

In our Physics & Astronomy labs, we use metersticks with great frequency. Often for measurements, sometimes to approximate distances that make the arithmetic easier, and occasionally as a handy tool for pointing to the projector screen.

They aren’t super-high precision any more than the rulers you remember from elementary school, and for that we have other tools. Sometimes, as you can see above, the years have warped and twisted things a bit. We adjust.

As you might expect, they offer metric distances on one side, inches and feet on the other. The best ones – the oldest set – were long ago painted black to conceal those SAE units. Clearly, someone grew weary of students measuring everything in inches and then complaining that the math wasn’t working out right.