Why It Was Almost Impossible to Make the Blue LED

I was watching a YouTube video from a Scottish YouTuber recently and heard him refer to a light as being a LED bulb. He, however, pronounced LED as if it were the element lead. I, an American, pronounce those bulbs as their three separate letters El Ee Dee, like an acronym. 

Neither, of course, is correct, nor is it at all relevant to this video.

This video, just over half an hour long and produced by Dr Derek of Veritasium, goes through the quantum mechanic explanation of how semiconductors conduct at room temperature which also explains how LEDs produce light and - eventually in the video - how LEDs can be tuned to produce different colors.

This video is also a great exploration of how doped semiconductors conduct electricity. 

I'm really happy that I don't have to teach this concept in my chemistry - or material science - classes because this really pushes my understanding of quantum mechanics and electronics. I didn't thoroughly understand it when I first heard about it back in 1993 or 1994, and I don't entirely understand it now. I do, however, fully accept that there are people who do understand these concepts and that we owe those people a massive debt because the widespread use of LEDs has been a huge revolution in energy savings for our world.

Plus it lets people wrap their cars in Christmas lights.

Where is he? We'll never know.

 

Source - Brewster Rockit

See, it's funny because it's a reference to the Heisenberg Uncertainty Principle in which - in a very simplified format - we can know the momentum or position of a particle but never both. 

I warn you, the uncertainty principle is a whole lot more complicated in its real form, but unless you're really into quantum mechanics, I recommend that you take the simple version instead.

With larger objects - say a person or a baseball - we can know the two quantities about the object almost perfectly, but as the object gets smaller - like atoms and protons and electrons or a shrunken Brewster Rockit - we can know less and less about the combination of the two quantities.

I get it. It takes some subtlety and understanding of the world of quantum mechanics to get the joke.

Luckily, I get the joke...like I got this other, similar one.

Why Are Soap Bubbles So Colorful?

The wave-particle duality of light is mind boggling to me, though it's not that impressive to most of my students.

The pretty colors of a soap bubble, on the other hand, unite us both in going, 'ooh, pretty."

Student Submitted - Hund's Rail

Source - C&EN

Today's post was submitted by Katelynn J, one of my AP chemistry students. As a sub assignment after the AP chemistry exam, I had students submit two posts for this blog. I'll be posting them over the next few weeks.

During COVID-19, this cartoon was probably especially relatable, since everyone was trying to stay as far away from each other as possible. Of course, staying healthy and safe is much more important than adhering to the buddy system, but when going into two separate cars, you’re sure to miss your travel companion at least a little.

In this specific comic, however, the problem isn’t social distancing, it’s Hund’s Rule. On the rail, representing the shells of the QMM, electrons after first fill up all empty spaces before being able to double up, since this stabilizes the atom. The two electrons here trying to enter a car together would make the atom unstable, so it’s better they stay apart.

Katelynn added that "I learned that Hund has more than one rule! His rules are best for the ground state of an atom, and all three have to do with electrons," and she found this website helpful for further reading.

Caption this...

I've sat this that shade, maybe not at that specific stadium but certainly at tennis matches where I've followed the sun and moved with the shade. In fact, if we started school a week or two later in the year, I'd likely be doing it for a week in August at the Cincinnati Open.

Sadly the picture isn't quite right in that the second row would need to be eight seats wide compared to only two seats for the first row. Or maybe four seats compared to one with people sitting on each other's laps to represent the Pauli Exclusion Principle. 

All that would need the shadow line to be shallower, more of a 15 or 20 degree angle rather than the 45 that's in this picture.

But then the sun wouldn't be as bright and harsh when it was that low in the sky meaning that the people likely wouldn't be seeking out the sun as overtly and urgently.

So maybe it's best not to question this but rather to chuckle at it and move on.

And definitely don't go listening to the "Electron Configuration Polka" by Michael Offutt.

I've been captcha-ed.

See, it's funny because there's no way to know where the electrons likely are in the quantum mechanical model of the atom. The best we can do is predict where the electrons will likely be found.

So, I'm going to fail that captcha.

Light sucking flames look like magic

I've posted about this black fire on the blog before.

This one - from Steve Mould - doesn't add a whole lot new to the basic technique of shining a sodium vapor light on a methanol (stay safe out there, folks) flame that has been doped with sodium chloride. It does add in some more information on how the spectra are created and some info about enchroma glasses (more on them next week).

Why is glass transparent? - Mark Miodownik

Mark Miodownik is the author of one of the better materials science books written for a popular audience, Stuff Matters. 

In that book he takes a chapter to explore each of the various material categories and some of that category's most common exemplars.

Here, however, Miodownik looks at glass to see why light can pass through it. Turns out it's all about electron transitions.

The Engineer Comedian - Don McMillan comedy (due to request)

Just let the comedy wash over you.

They're all funny, but I really enjoy the third joke. I'm in the really small overlap area, apparently.

The Hidden Science of Fireworks

I feel like some of the above video was from some of Veritasium's previous videos because they look somewhat familiar to me.

With that being said, the video does a great job explaining what happens in fireworks.

Dr Derek starts with making rudimentary black powder (gunpowder - not the modern, smokeless version as Derek explains at 8:30) starting with the initial recipe from ancient China and moving to a more modern 75/10/15 ratio of carbon/sulfur/charcoal and then to a commercial, modern gunpowder. 

From there, it's onward to testing the effects of container strength on the size of the explosion - first with a simple, cardboard tube then with a reinforced tube. He then brings in a fireworks manufacturer who explains the cardboard, spherical shells of actual fireworks and the method for launching them. 

Then a bit about the methods of triggering the shells - showing black match then the craft-paper-encased quick match - including how to waterproof that trigger and how that trigger moves into the fireworks shell itself and lights the stars to produce the color and flash.

Speaking of the stars, they move into the creation of the different colors due to metallic salts and showing the individual spectra of those elements due to their electron configuration. The expert does then use some methanol to step things up a bit. (Remember kids, don't use methanol...ever.)

And the video wraps up with footage of a drone flying through the fireworks finale. I'll admit...that's pretty cool and should absolutely be watched in high res and expanded size.

Solar System Model

 

Rollover joke - The Earth is, on average, located in the habitable zone, but at any given time it has a certain probability of being outside it, which is why life exists on Earth but is mortal. (Source - XKCD)

See, it's funny because most of the time, the atom - particularly the Bohr model of the atom - is likened to the solar system with electrons following 'orbital' paths around the nucleus the way that planets follow similar paths around the sun.

As a chemistry teacher, I can say that it's much, much harder to come up with a similarly easily understood analogy for how electrons exist in the quantum mechanical model of the atom. There just isn't any sort of macroscopic thing that is anything like the quantum mechanical model of the atom.

And if the planets did move like electrons, that would be somewhat terrifying - especially as electrons can teleport from region to region a la an electron in a box.

Though I do have some evidence that the planets have a measurable spin, so there is that, at least.

In Space, No One Can Stop You From Welding

Cold welding is frickin' weird.

Richard Feynman wrote (or said in a lecture - I'm not sure which), "when the atoms in contact are all of the same kind, there is no way for the atoms to 'know' that they are in different pieces of copper. When there are other atoms, in the oxides and greases and more complicated thin layers of contaminants in between, the atoms 'know' when they are not on the same part."

But two metallic pieces that don't have those thin layers between them - primarily because they've been in space and rubbing against each other - can spontaneously weld together to become a single piece of metal.

It's possible to get that to happen on Earth, but it's not easy because of all the pesky oxygen we have around us all the time.

Metals are way weirder at the quantum level than we think they are, man.

Spooky

Source - http://www.threepanelsoul.com/comic/spooky

See, it's funny because Schrödinger's (the umlaut is important, don't forget it) cat is a famous thought experiment in which a hypothetical cat is placed in a hypothetical box along with a flask of poison, a radioactive source, and some kind of monitor that detects radioactivity. If the monitor detects radioactivity (something that happens with 50% frequency in a certain amount of time), the monitor breaks the flask with the poison, killing the cat. If not, the flask remains unbroken, and the cat lives.

Until the box is opened, however, the cat's fate is unknown, leading to a quantum superposition in which the cat is both alive and dead until the box is opened, collapsing the two possibilities into one reality.

It's a thing that shows up in popular culture from time to time, most famously on the AWFUL SERIES The Big Bang Theory.

But here's the deal, yo...

Schrödinger wasn't in favor of the thought experiment. He didn't like it. He was using it to suggest that the idea of quantum superposition was absurd.

From wikipedia...

Schrödinger did not wish to promote the idea of dead-and-alive cats as a serious possibility; on the contrary, he intended the example to illustrate the absurdity of the existing view of quantum mechanics.

...

It is typical of these cases that an indeterminacy originally restricted to the atomic domain becomes transformed into macroscopic indeterminacy, which can then be resolved by direct observation. That prevents us from so naïvely accepting as valid a "blurred model" for representing reality. In itself, it would not embody anything unclear or contradictory. There is a difference between a shaky or out-of-focus photograph and a snapshot of clouds and fog banks.

...

(Written by Einstein to Schrödinger) You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality, if only one is honest. Most of them simply do not see what sort of risky game they are playing with reality—reality as something independent of what is experimentally established. Their interpretation is, however, refuted most elegantly by your system of radioactive atom + amplifier + charge of gun powder + cat in a box, in which the psi-function of the system contains both the cat alive and blown to bits. Nobody really doubts that the presence or absence of the cat is something independent of the act of observation.

So, I would imagine that Schrödinger would be appalled that his non-scientific legacy has come down to people knowing him for a theoretical experiment that he came up with in an attempt to point out how ludicrous quantum superpositions are.

And I love the idea that Schrödinger's ghost haunts the world embracing anyone who recognizes that 'his experiment' is ridiculous and stupid.

That was his point.

(Though I would be remiss if I didn't point out that quantum superpositions have turned out probably to be 100% true and real.)