At 2:43 PM -0500 7/27/01, drs wrote:
12:39 AM 7/25/2001 -0500, Jim Choate wrote: On Tue, 24 Jul 2001, Tim May wrote:
IAAP, so let me make a suggestion. Don't argue about physics. The winner comes down to the person or persons least wrong since every description given so far is an attempt to extend some part of an incomplete picture in a way that is _WRONG_, leading to arguments about misstatements.
You're a twerp worse in many ways than Choate is. I expect he will embrace you as his new ally. After this message, you will reside in my kill file.
Scattering is not reflection. In fact, photons do lose energy scattering and the first experiments that demonstrated this is where scattering gets its name: Compton scattering. The compton scattering formula is easily derived from conservation of 4-momentum. Reflection from a mirror is easily described by maxwell's equations, but is more difficult in terms of photons. While the description of the photoelectric effect is more or less ok, the term "thermalize" means applies to contimuum scattering of electrons in the conduction band through collisions with other electrons, not to discrete transitions. Describing a reflection as scattering can be done, but not in the length of this response.
Yeah, and not in the length of _my_ response. I used "scattering" as the shorthand name for all of the physics of incident photons being returned or thermalized: pure reflections, reflections off of asperities, and even absorbtion in the target. There are at least three major domains for discussing Choate's claim that photons hit a target, "lose some energy," and are then re-emitted at some lower energy: * Domain 1: Newtonian physics. Light of some color is reflected at the same color, minus absorbed frequencies. (Blue light reflects as blue light, never as red light.) Angle of incidence equals angle of reflection, etc. * Domain 2: Maxwell's equations. Same basic physics, but more nuanced in terms of E and H fields, more details about how conductors and dielectrics respond to incident photons. Nevertheless, same results predicted as in Domain 1. * Domain 3: Semi-philosophical stuff about whether the incident photon is the "same" as the returned photon. Issues of whether photons are really waves or corpuscles. Again, no deviation from Domain. Regardless of which domain one spends time in, the notion that a "blue photon" loses energy and is downshifted in frequency is SIMPLY NOT OBSERVED. Whether one cites just the observations, that reflections do do NOT shift the frequencies of monochromatic light (what I call in shorthand "blue photons"), or one cites quauntum theory (no partial losses of photon energy, basically), the fact is that Choate is incorrect in claiming that photons lose energy (frequency) when reflecting or scattering off of mirrors. Beams may lose _intensity_, as some photons scatter at wide angles (not with the main angle of reflection, in other words), or are absorbed and thermalized by the mirror itself. But the photons DO NOT lose energy due to the "resistance" and the "induced currents." A naive reading of some physics texts, even Jackson's "Classical Electrodynamics," might suggest to the naive reader that some weird interaction and ohmic loss might "downshift" the frequency of photons, but experiments show no such downshift, In fact, Einstein got the Nobel for explaining why photons don't lose ANY energy except when they lose ALL of their energy via the photoelectic effect.
Let me suggest that everyone defer to "Classical Electrodynamics" by Jackson, as a definitive reference. It's the canonical physics text on the subject and is practically universal as the text for a first year graduate course in any physics program. If you know anyone that's a physicist, they should have a copy.
Which I used in 1973. As for your sentiments about how _both_ of us are wrong, you're an ass. P L O N K. Have fun with Jim Choate as your new best friend. --Tim May -- Timothy C. May tcmay@got.net Corralitos, California Political: Co-founder Cypherpunks/crypto anarchy/Cyphernomicon Technical: physics/soft errors/Smalltalk/Squeak/agents/games/Go Personal: b.1951/UCSB/Intel '74-'86/retired/investor/motorcycles/guns