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From a book intro I've been reading, Scattering, Absorption and Emission of Light by Small Particles by Mishchenko, it states that when incident light hits a particle, that particle may absorb light, scatter light or emit the light.
Excerpt:
Can anyone explain to me, on a physical level, the difference between emission (referred in the book as thermal emission if the particle is above absolute zero) and scattering (whether its described by Mie or Rayleigh, I am looking for physical intuition rather than mathematical theory).
I'm also confused by the scattering process in the sense that many authors describe what is happening by (as above):
extinction = absorption_s + scattering.
Is this "absorption_s" term related to the absorption you get during emission like in spontaneous and stimulated emission or is it describing something else? There was one source that said it referred energy being absorbed by the particle but lost during collisions, but this didn't explain how the energy was absorbed.
Any help much appreciated
Excerpt:
A parallel monochromatic beam of light propagates in a vacuum without any change in its intensity or polarization state. However, interposing a small particle into the beam, as illustrated in panel (a) of the diagram on the next page, causes several distinct effects. First, the particle may convert some of the energy contained in the beam into other forms of energy such as heat. This phenomenon is called absorption. Second, it extracts some of the incident energy and scatters it in all directions at the frequency of the incident beam. This phenomenon is called elastic scattering and, in general, gives rise to light with a polarization state different from that of the incident beam. As a result of absorption and scattering, the energy of the incident beam is reduced by an amount equal to the sum of the absorbed and scattered energy. This reduction is called extinction. The extinction rates for different polarization components of the incident beam can be different. This phenomenon is called dichroism and may cause a change in the polarization state of the beam after it passes the particle. In addition, if the absolute temperature of the particle is not equal to zero, then the particle also emits radiation in all directions and at all frequencies, the distribution by frequency being dependent on the temperature. This phenomenon is called thermal emission.
Can anyone explain to me, on a physical level, the difference between emission (referred in the book as thermal emission if the particle is above absolute zero) and scattering (whether its described by Mie or Rayleigh, I am looking for physical intuition rather than mathematical theory).
I'm also confused by the scattering process in the sense that many authors describe what is happening by (as above):
extinction = absorption_s + scattering.
Is this "absorption_s" term related to the absorption you get during emission like in spontaneous and stimulated emission or is it describing something else? There was one source that said it referred energy being absorbed by the particle but lost during collisions, but this didn't explain how the energy was absorbed.
Any help much appreciated