The answer to your questions depends on the level of understanding of quantum mechanics. I am sending info where to find the subject discussed in more details.
Bernhard Rupp's book page 251 necessarily simplifies a rather complex subject of the photon's interaction with multiple particles. Quantum mechanical wave function can be considered virtual from the measurement process point of view, as the photon (a single quantum) appears in the detector during the measurement process, but not on the way to it. > the photon's coherence length The concept of photon's coherence length involves quantum mechanics mixed state. For introduction see: http://en.wikipedia.org/wiki/Quantum_state#Mixed_states > virtual waves Quantum mechanical wave function is "virtual" in certain sense. The Feynman Lectures on Physics Vol 3 covers this subject quite well. > appears again in some direction This refers to quantum mechanical wave-particle duality > Hello Everybody! > I was trying to make some sense from Bernhard Rupp's book page 251. > > I will copy the relevant part... > > When photons travel through a crystal, either of two things can happen: (i) > nothing, which happens over 99% of the time; (ii) the electric field vector > induces oscillations in all the electrons coherently within* the photon's coherence length* ranging from a few 1000 Angstroms for X-ray emission lines to several microns for modern synchrotron sources. At this point, the > photon ceases to exist, and we can imagine that the electrons themselves emanate *virtual waves*, which constructively overlap in certain directions, and interfere destructively in others. The scattered photon then *appears again in some direction*, with the probability of that appearance proportional to the amplitude of the combined, resultant scattered wave in that particular direction.......The sum of all scattering > events of independent, single photons then generates the diffraction pattern. > > I underlined the problematic parts... > > can anyone shed some light on this ..or point me in the right direction? > > > Thanks in advance > Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353 Zbyszek Otwinowski UT Southwestern Medical Center at Dallas 5323 Harry Hines Blvd. Dallas, TX 75390-8816 Tel. 214-645-6385 Fax. 214-645-6353
