electrons

4 Articles

The Stern-Gerlach Experiment Misunderstood

December 13, 2024 by 15 Comments

Two guys — Stern and Gerlach — did an experiment in 1922. They wanted to measure magnetism caused by electron orbits. At the time, they didn’t know about particles having angular momentum due to spin. So — as explained by [The Science Asylum] in the video below — they clearly showed quantum spin, they just didn’t know it and Physics didn’t catch on for many years.

The experiment was fairly simple. They heated a piece of silver foil to cause atoms to stream out through a tiny pinhole. The choice of silver was because it was a simple material that had a single electron in its outer shell. An external magnet then pulls silver atoms into a different position before it hits some film and that position depends on its magnetic field.

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Neopixels? Try Liquid Nitrogen To Color Shift Your LEDs Instead

November 11, 2023 by 23 Comments

If you’re like us, you’ve never spent a second thinking about what happens when you dunk an ordinary LED into liquid nitrogen. That’s too bad because as it turns out, the results are pretty interesting and actually give us a little bit of a look at the quantum world.

The LED fun that [Sebastian] over at Baltic Lab demonstrates in the video below starts with a bright yellow LED and a beaker full of liquid nitrogen. Lowering the powered LED into the nitrogen changes the color of the light from yellow to green, an effect that reverses as the LED is withdrawn and starts to warm up again. There’s no apparent damage to the LED either, although we suppose that repeated thermal cycles might be detrimental at some point. The color change is quite rapid, and seems to also result in a general increase in the LED’s intensity, although that could be an optical illusion; our eyes are most sensitive in the greenish wavelengths, after all.

So why does this happen? [Sebastian] goes into some detail about that, and this is where quantum physics comes into it. The color of an LED is a property of the bandgap of the semiconductor material. Bandgap is just the difference in energy between electrons in the valence band (the energy levels electrons end up at when excited) and the conduction band (the energy levels they start at.) There’s no bandgap in conductive materials — the two bands overlap — while insulators have a huge bandgap and semiconductors have a narrow gap. Bandgap is also dependent on temperature; it increases with decreasing temperature, with different amounts for different semiconductors, but not observably so over normal temperature ranges. But liquid nitrogen is cold enough for the shift to be dramatically visible.

We’d love to see the color shift associated with other cryogens, or see what happens with a blue LED. Want to try this but don’t have any liquid nitrogen? Make some yourself!

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The Fine Structure Constant In A Blink

May 7, 2021 by 8 Comments

Electronics is really an applied branch of physics, so it isn’t surprising that if you are serious about your electronics, you probably know a little physics, too. If you’ve ever heard the term “fine structure constant” and weren’t entirely sure what it means, [Parth G] wants to explain it to you in about a minute. His video explanation appears below.

You may know that the constant, often represented by α, is approximately 1/137, but what does that mean? The answer relates to the orbit of electrons. You might remember from school that electrons orbit in shells around the nucleus.  That is, an atom might have some electrons in the innermost shell, and more electrons in an outer shell.

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Back To Basics: What’s The Deal With Magnets?

November 20, 2015 by 82 Comments

I consider myself a fairly sharp guy. I’ve made a living off of being a scientist for over 20 years now, and I have at least a passing knowledge of most scientific fields outside my area. But I feel like I should be able to do something other than babble incoherently when asked about magnets. They baffle me – there, I said it. So what do I do about it? Write a Hackaday post, naturally – chances are I’m not the only one with cryptomagnetonescience, even if I just made that term up. Maybe if we walk through the basics together, it’ll do us both some good understanding this fundamental and mysterious force of nature.

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