photons and reflection
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From: RichD on 27 Nov 2009 19:24 According to the wave theory of light, angle of incidence equals angle of reflection. No problem, in theory or fact. However, per QM, light falls as a 'rain' of photons. What happens then? As I understand it (big qualifier there), the photons are absorbed by surface atoms. Electrons jump to higher energy orbitals, then fall back to ground state, emitting photon(s) of its characteristic spectrum. Simple.... This raises several questions, regarding geometry... the aforementioned angles are defined relative to a surface normal. But the surface is not truly continuous, it's atomic and chunky. How does an atom know where the 'normal' is? How does it know which direction to fire its photons, after a time delay? Does it have some sort of 'light momentum' memory? I never studied quantum field theory, maybe it's explained there... -- Rich
From: Phil Allison on 27 Nov 2009 19:35 "RichDope" > > According to the wave theory of light, angle of > incidence equals angle of reflection. No problem, > in theory or fact. > > However, per QM, light falls as a 'rain' of photons. > What happens then? As I understand it (big qualifier > there), the photons are absorbed by surface atoms. > Electrons jump to higher energy orbitals, then fall > back to ground state, emitting photon(s) of its > characteristic spectrum. Simple.... ** Think you need to read up on how reflection of light really works. Cos what you describe above sounds more like how a light pumped gas laser works. http://en.wikipedia.org/wiki/QED_(book) ..... Phil
From: Salmon Egg on 27 Nov 2009 23:05 In article <7d8aade9-635f-4ef9-9c04-ebafbc5b7a42(a)o13g2000vbl.googlegroups.com>, RichD <r_delaney2001(a)yahoo.com> wrote: > According to the wave theory of light, angle of > incidence equals angle of reflection. No problem, > in theory or fact. > > However, per QM, light falls as a 'rain' of photons. > What happens then? As I understand it (big qualifier > there), the photons are absorbed by surface atoms. > Electrons jump to higher energy orbitals, then fall > back to ground state, emitting photon(s) of its > characteristic spectrum. Simple.... > > This raises several questions, regarding geometry... > the aforementioned angles are defined relative > to a surface normal. But the surface is not truly > continuous, it's atomic and chunky. How does an > atom know where the 'normal' is? How does it > know which direction to fire its photons, after a > time delay? Does it have some sort of 'light > momentum' memory? > > I never studied quantum field theory, maybe it's > explained there... > > -- > Rich Quantum Electrodynamics does indeed explain. Feynman wrote a book (with help because he hated the effort required to write books) s entitled QED to cover the topic. My guess is that there still is a series of lectures given at the University of Auckland on-line. Googke for it. Bill -- An old man would be better off never having been born.
From: nuny on 28 Nov 2009 00:03 On Nov 27, 4:24 pm, RichD <r_delaney2...(a)yahoo.com> wrote: > According to the wave theory of light, angle of > incidence equals angle of reflection. No problem, > in theory or fact. Not just the relatively new wave theory. "Snell's" law and ray theory go back to Alhazen. > However, per QM, light falls as a 'rain' of photons. > What happens then? As I understand it (big qualifier > there), the photons are absorbed by surface atoms. > Electrons jump to higher energy orbitals, then fall > back to ground state, emitting photon(s) of its > characteristic spectrum. Simple.... Not really *that* simple. The presence of electrons' charges absorbs some energy from passing photons and slows them down; the charges then oscillate out of phase with the photons, generating their own alternating field which interferes with the incoming photons. The resultant of the interference, with the same frequency but shorter wavelength as the incoming photons, then is either transmitted into the material containing the electrons, or reflected out of it, depending on the angle of incidence. > This raises several questions, regarding geometry... > the aforementioned angles are defined relative > to a surface normal. But the surface is not truly > continuous, it's atomic and chunky. How does an > atom know where the 'normal' is? How does it > know which direction to fire its photons, after a > time delay? Does it have some sort of 'light > momentum' memory? Transmission, reflection, and refraction at a surface are governed by the ratios of the refractive index on both sides of the surface. The whole atom does not reflect photons, the electrons do, and orbitals are distorted by being involved in bonds that hold atoms together. An atom's electrons on the surface of an object see half of the universe as "constricted" by the fields of other atom's electrons, the other half as "free" of that constriction. The photons' energy can't be held onto by the electrons forever, they _have_ to let go of it, and the most likely direction is that with the lower index. Very roughly speaking. > I never studied quantum field theory, maybe it's > explained there... Hope that helps. Mark L. Fergerson
From: Skywise on 28 Nov 2009 00:05
RichD <r_delaney2001(a)yahoo.com> wrote in news:7d8aade9-635f-4ef9-9c04- ebafbc5b7a42(a)o13g2000vbl.googlegroups.com: > I never studied quantum field theory, maybe it's > explained there... I will add my voice to the recommendation of QED by Feynman. It was a very enjoyable read, and you don't need to be a math major to comprehend it, as there is no math. Brian -- http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html Sed quis custodiet ipsos Custodes? |