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The Centenary Of Quantum Physics
OCatenac writes: "This article at the Economist regarding the 100th anniversary of Max Planck's discovery of Quantum Physics is interesting. Thought other /. readers might find it interesting too."
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Actually, you are a bit mistaken
ultraviolet catastrophe . . . exponentially more radiation as the wavelength got shorter.
You mean the infra red catastrophe. but names make no difference. what is important is that classical calculations predict exponential increases in radiation at longer wavelengths. This is in fact why light bulbs are yellow, and not more red. It is because the peak of the plank spectrum at the temperature that incandescant bulbs are at is in the yellow part of the spectrum
there are also some minor problems with your other explanations, however, I do agree with you that journalists should know what they are talking about before they write.
Quando Omni Flunkus Moritati
The Rayleigh-Jeans spectral distribution of blackbody radiation has the form required by Wein's law: the energy density varies with the inverse fifth power of the wavelength. This leads to an exponential increase in energy density with decreasing wavelength, which is referred to as the "ultraviolet catastrophe," just as the previous poster said (what's catastrophic is the complete failure of the Rayleigh-Jeans spectrum, which is a necessary consequence of classical physics).
Pick up any introductory modern physics text -- it will say precisely what I (and dmatos) just did.
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Politics is about making compromises. Religion isn't. --Michael Horton
...probably wouldn't know a quanta if it jumped up and bit him in the ass.
First of all, Planck did not discover quantum mechanics. He postulated quantized energy levels. That's all. Of course, perhaps he did discover quantum mechanics. I can see him now, in a dusty library, in some dark corner that no-one has been in for centuries. He trips on a tome that someone has carelessly left in the middle of the aisle, and crashes into a bookcase. After the ensuing chaos, what lands on his lap but the volume "Quantum Physics, a Beginner's Guide." Perhaps then you could say he "discovered" quantum physics.
Secondly, anyone who has ever looked at a physics text book knows that quantized energy levels explain the ultraviolet catastrophe, not why a light bulb is yellow, for chrissake! Classical calculations show that a radiating blackbody would have exponentially more radiation as the wavelength got shorter. Not only is this not what is observed, but it would lead to infinite energy being radiated by the blackbody. It was Planck's postulation that energy levels were quantized that resolved this.
Now, I wonder if the author of this article can tell me how the wave-nature of electrons is used to make lasers and LED's? LED's work as they do because Gallium Arsenide is a direct bandgap material, meaning that in order to transition from the valence band to the conduction band (take a course on the electrical properties of materials) the electron only needs energy, as opposed to in silicon where it needs both energy and momentum. That means that it is easier for an electron to drop back down from conducting band to valence band in GaAs, emitting only energy - read this as light. Nowhere does the wave nature of the electron come into this. Laser diodes are based on the same principle. Go read a book.
As for the description of how a transistor works, that is a hell of a lot of bullshit. He's correct in the fact that a transistor consists of electron rich and electron poor (commonly called n-type and p-type doped semiconductors) regions, but there is no way to prevent there from being a gradient in between these regions. His Schrodinger equation explanation is also crap. Apart from the infinite potential well problem, there is a solution to the Schrodinger equation for every point in space. It is just required to be continuous and smooth (ie, first and second derivatives must exist). Right now, transistors work because of potential. When you apply the necessary voltage to the gate of a transistor, it attracts enough electrons or holes (opposite of electrons when studying materials) to allow a conductive pathway between the source and the drain. This is true for BJT's and most FET's. The other option is that the gate voltage will drive away the electrons or holes, and "pinch off" the current. This is how a JFET works.
Dammit, I really wish that these "journalists" would pick up a text book before they write crap like this.
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