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Energy and momentum are conserved. If one photon enters one side of an atom and only one photon exits the other side, then either the exit photon has the same energy and momentum as the entry photon (including exactly the same direction), or some momentum and energy are left behind in the atom, perhaps in the form of lifting an electron to a higher orbital.
A photon reflecting perpendicularly off of a massive mirror surface reverses its direction. This imparts very slightly less than twice the photon's initial momentum to the mirror, and the photon rebounds with very slightly less momentum than it had. If the mirror's mass is 1 kg, its velocity changes by It's energy changes by J, which is times the photon's energy. The reflected photon's wavelength is increased by a factor of ). This is generally considered insignificant.
Bear with me for a moment, consider for instance the emission spectrum of hydrogen, can we assume that the hydrogen atom possesses only one electron ? If so how do you explain the emission spectrum of hydrogen which contains blue , green blue, red etc light each having distinctive frequencies. If it were an atom with multiple electrons there might be latitude for some confusion, however since there is only one electron involved,
it follows ( indeed if any attempt is to be made to be logical, it must follow) that, if for instance the excited hydrogen atom is emitting blue light at 500 nm and a frequency of 6 x 10 14 Hz, it follows that this must be due to that single electron oscillating back and forth at just those frequencies(i.e., at the rate of times a second)? Following this line of reasoning further if the electron in the hydrogen atom can oscillate at such frequencies isn't it possible that electrons in more complicated atoms possessing multiple electrons, have the same capability? Now before you state that the frequency of the photon has nothing at all to do with it. Consider for instance the generation of Microwaves with frequencies of 10 13 Hz, if it is possible for a man made device to create oscillations at 10 13 Hz , what makes it so impossible for an electron within an atom to oscillate at frequencies of 10 14 Hz. In fact to deny such a possibility, which is apparently what you are doing if I am not mistaken, is totally unreasonable. Would you agree with this statement ? In spite of the fact that it might be claimed that gravity waves have been found, there still seems to be some confusion on the mechanism of photon emission and the one off scenario that your post seems to imply apparently has widespread support.
why even consider a mechanism where the photon's wave-length is increased by a factor of , when in the first place such an insignificant (to us) difference, might be considerable for a photon and in the second place is totally unnecessary, a competent working mechanism of absorption and emission being already in place. Why have a separate process for reflection and a separate process for scattering, when patently, there is absolutely no sane reason for it ?
http://www3.uji.es/~planelle/APUNTS/ESPECTROS/jce/JCEphoto.html - This is a very thorough explanation of absorption of photons with quicktime videos.http://madsci.org/posts/archives/2004-04/1082128751.Ph.r.html - This is a more direct answer to your question.http://webpages.ursinus.edu/lriley/courses/p212/lectures/node40.html - This is another explination of the absorption process.The gist of the above is that in order for an electron to transition from one state to another it has to enter a supposition of the initial and final state. The resulting supposition is no longer time independent and evolves over a finite amount of time from being more initial state to being more final state with significant oscillations. The result for an electron in an atom is that the electron cloud changes shape in an oscillatory manner with a frequency that matches the light being emitted or absorbed. The reason most physics courses don't talk about this processes is because it requires some pretty complicated mathematics (even by Quantum standards) and in general you can calculate everything you are likely to need to know about the absorption of a photon without ever detailing the processes. Most physical observables of interest like the energy of the photon can be calculated from the time independent stationary states so there is no reason to bother with the more complicated stuff.
Why have a separate process for reflection and a separate process for scattering, when patently, there is absolutely no sane reason for it ?
A single hydrogen atom will only emit one photon at a time. The different frequencies available can be explained by there being multiple energy levels available, between which the electron can move. The reason the emission spectrum of hydrogen has multiple lines is because the samples used always have many atoms (I would be surprised if there were many measurements made on collections of fewer than 1010atoms, and therefore 1010 electrons involved...)
A mirror's silver layer provides a constant-voltage surface. When a photon hits that surface, the outer electrons of the silver atoms move about in such a way that their combined electric fields together with the incoming photon add up to a constant-voltage surface. Subtracting the electric field of the incoming photon yields the electric field of a virtual photon continuing along the incoming photon's path and disappearing into the depths of the mirror's virtual image. When the electrons rebound to their equilibrium positions, they emit a real photon; and angle of incidence equals angle of reflection.
The oscillations that occur in the electron wave function during a transition exactly match the oscillations of the incoming or outgoing photon.
Reflection and scattering are precisely the same thing. Reflection is just scattering from a lot of atoms all arranged in a very uniform way such that the resulting scattering is also very uniform and reinforces itself.
What is the difference between the scattering of photons and the reflection of photons.
What are these Photons you speak of?
In respect to a Photon, a Photon travels a linear path at the speed of the light (c) .
chiralSPOQuote A single hydrogen atom will only emit one photon at a time. The different frequencies available can be explained by there being multiple energy levels available, between which the electron can move. The reason the emission spectrum of hydrogen has multiple lines is because the samples used always have many atoms (I would be surprised if there were many measurements made on collections of fewer than 1010atoms, and therefore 1010 electrons involved...) May I request you, just for a moment to take your nose out of your books and say, take a walk around the garden or to sit and admire a favourite piece of furniture, its shape its colour and so on. Or even just look around at the clutter on your desk, the pens, the covers of books, maybe the mouse pad. Try to imagine that all this wonderful, terrific wealth of information is being delivered to your senses by one atom, emitting one photon at a time, if you can succeed in doing this you are truly a magi of Quantum Mechanics, one of the consecrated ! If after this exercise you still feel that your impossible to ascertain statement is true, then well and good, my reasoning must be at fault and I will have to re-think my ideas.