Two Great (but Old) Videos about Waves

I've had both of these videos on the SolderSmoke blog already, but an e-mail from Farhan reminded me how good they both are. If you are averse to older material you might not want to watch -- but you would be missing out on some wisdom.  

 

How Big is a Photon? (Video)

As I have mentioned in the podcast and in blog posts, I have a lot of trouble picturing HOW 20 meter photons somehow fly off my antenna.   I understand how EM WAVES are generated.  But there doesn't seem to be any corresponding explanation for how the photons are generated.  

This video looks at a related question:   How BIG are the photons of visible light?   I am not sure this is all correct (and neither, apparently, is the creator of this video) but it is very interesting.  

Comments are welcome.  

Electromagnetic Waves -- Sir Lawrence Bragg -- Royal Institution (Video)

This is a really wonderful video.  I especially liked his presentation on the nature of the EM spectrum, and his use of the centimeter waves to demonstrate wave behaviour.   The two slit experiment was very nice.  Sir Lawrence's presentation on SWR was brilliant.  

Still, you wonder how would all this be done if those waves of Sir Lawrence (and Young, Maxwell and Faraday) were considered to be the photons that they also really are? 

In any case, three cheers for the Royal Institution: https://soldersmoke.blogspot.com/search?q=Royal+Institution  

Understanding Maxwell's Equations (video)

And you should also look at the accompanying web site: 

https://www.maxwells-equations.com/m/index.php#maxwells

Writing about the equations, the author notes, "They are formidable to look at - so complicated that most electrical engineers and physicists don't even really know what they mean.  This leads to the reason for this website - an intuitive tutorial of Maxwell's Equations. I will avoid if at all possible the mathematical difficulties that arise, and instead describe what the equations mean. And don't be afraid - the math is so complicated that those who do understand complex vector calculus still cannot apply Maxwell's Equations in anything but the simplest scenarios. For this reason, intuitive knowledge of Maxwell's Equations is far superior than mathematical manipulation-based knowledge. To understand the world, you must understand what equations mean, and not just know mathematical constructs. I believe the accepted methods of teaching electromagnetics and Maxwell's Equations do not produce understanding. And with that, let's say something about these equations." 

Thanks to Armand WA1UQO for sending me the wonderful book about Faraday and Maxwell that put me -- once again -- on the path toward a deeper understanding of their work.  

https://www.amazon.com/Faraday-Maxwell-Electromagnetic-Field-Revolutionized/dp/1633886077/ref=sr_1_1?crid=1ZRPDYCCN9CGA&keywords=Faraday+and+Maxwell+Forbes+Mahon&qid=1690716355&s=books&sprefix=faraday+and+maxwell+forbes+mahon%2Cstripbooks%2C55&sr=1-1

Thanks also to Michael Rainey AA1TJ.  Several years ago he commented that he too wanted to get a better understanding of these equations. 

Inductive Reactance and Special Relativity

Bill,

I'd been meaning to share these stories with you after I read your book a couple years ago but I never got to it.  I thought you might enjoy them, from an "engineering perspective", I guess.

One of the courses I had to take for my undergrad was an engineering physics type class.  I loved it.  I think a lot of hams seem to have more curiosity about the physics of electronics than regular non-ham engineers, at least that's how it's always seemed to me.  Anyway, I'm sending you a snapshot of the relativistic length contraction figure in the book "Concepts of Modern Physics", 4th Ed by Arthur Beiser.  I thought you'd enjoy it as it is almost identical to what you mentioned in Soldersmoke (from your "Atoms to Amperes" book I think).

Hopefully there's enough resolution there to make it out.  Basically, when you flow current in the same direction in both wires, they attract.  That's because the electrons see effectively many more positively charged nuclei from the other wire than they do other electrons due to the nuclei distances being compressed by the Lorentz-Fitzgerald contraction (later refined by Einstein). 

When I first saw this, in my early 20s, I was completely floored!  Nowhere had I ever learned anything like this from the ham license manuals or even my basic physics course.  The implications were also very profound -- magnetism was nothing more than electrostatic attraction, the attraction between charges.  The "electromagnetic" force was really just an electric force.  Relative motion between charges gives the illusion of "magnetism". 

Much later, I listened to some of the old Feynmann lectures.  In them at one point he adamantly proclaimed that there's only the electric force between charges, and there is no magnetic force!  I still find this confusing.  Recently I brought this up to a university RF engineering professor.  I wondered why we dealt with Maxwell's equations when in reality the magnetic field is an illusion.  The "real" formulas come from Feynmann's theory of quantum electrodynamics!  His reply was something along the lines of Maxwell's equations being a solution of quantum theory that worked well for our purposes.  To be honest, I didn't really understand his reply and I'm still skeptical!  I think his point was that the QED calculations are overly complicated and unnecessary for most problems we deal with, things like patterns from an antenna.  I don't think Maxwell's equations appropriately describe things like lasers though, which are more quantum in nature with the coherent beam.

FYI, most engineering students I ran across had only passing curiosity for these things.  Only in graduate school did I start to find people curious enough to really try to understand "what lies beneath" some of this stuff, mainly this physics.  Honestly not even everyone in grad school was all that captivated.  As you've said before, there's a lot of "turn the crank" mentality in engineering where you wade through mathematics to get answers, not always thinking about the physics.  It's even worse in the digital world, where everything gets boiled down to computer code! 

One more quick thing.  I talked to a physics prof once, asking him if there was any research happening in his department focused on electromagnetics and radio waves, etc.  His reply: "radio waves are nothing more than the result of accelerating electrons".  Period!  Discussion over.  In other words, that's ancient history.  Engineers are still very much involved with new technologies involving antennas and amplifiers, etc.  But as far as the physicists are concerned, I get the impression that our whole field is pretty ho-hum.  But he was right about accelerating electrons, I also found out later.  And it doesn't have to be electrons.  Anything carrying charge undergoing acceleration will emit photons.  That's another crazy situation that I only more recently learned.

Hope that was entertaining!

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A COOL Norwegian "S" Meter (video)

Immaterials: Light painting WiFi from Timo on Vimeo.

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"Chart of Electromagnetic Radiations"

Wow, all you need to know, right here on one poster!  They even cover particle/wave duality.  I tried printing it up in hi-res but the uncertainty principle seems to be interfering! Get yours here:  http://www.flickr.com/photos/llnl/9403051123/sizes/l/ 


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Imaging Across the EM Spectrum

Amazing images here:

http://blog.makezine.com/2013/04/09/somewhere-outside-the-rainbow-imaging-across-the-em-spectrum/

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Seeing EM Waves with a Coffee Can

Thanks to Leif KC8RWR for alerting me to this. Amazing stuff, but somehow I think they need to get an Altoid tin into this project. You can sense the enthusiasm.

"Particles? We don't need no stinkin' particles!"

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20