These are just examples of the same thing. Now i just saw a car painting, that was made so, that from different angles, the car's certain parts appeared in different colors, and if you moved, the car appeared to change colors. You know, there are those materials, where from a certain angle, you can see a picture, but not from a certain other angle. In this case, like a wall, or a material that has a lattice structure, it is basically depending on the structure of the lattice atoms, how they reflect the photons, in random ways, but these random ways might even create certain phenomenons, where the wall facing you will appear darker. That is why that a wall facing away from you (but towards the light) might absorb more non-visible photons by the surface, and then those photons get re-emitted in multiple steps and some of them as visible light creating an effect as if the wall was brighter. With absorption and re-emission, it happens, that even non-visible wavelength photons get absorbed by the surface and then they are re-emitted in multiple steps, in different wavelength photons, some of which will be visible light. Now there is one more thing in the case of diffuse reflection. It has nothing to do with the angle of incidence. Now the reason why the brightness of the wall facing towards you might be darker then the wall facing a little bit away from you is because even though more light should be reflected towards you from the wall facing towards you, the photons on that wall will have diffuse reflection, in which case the angle of reflection is random. That is why in this case you do not get a mirror image, but a faded reflection. Now in this case, the photons do not keep their original angle of incidence, and do not keep their relative angle nor their relative phases nor their energies. In the case of diffuse reflection, most of the visible wavelength photons are absorbed by the surface atoms in the lattice, and then re-emitted. Yes it is possible, because walls are typically creating diffuse reflection. Now you are saying that it is possible that a wall that is facing towards you is appearing darker then a wall that is facing a little bit away from you. In the case of diffuse reflection, like a wall, you might either see the wall facing towards you lighter or darker then the wall facing a little bit away from you, this is the case you are referring to In the case of specular reflection, a mirror or a shiny metal, you will always see the mirror facing towards you lighter, then the mirror facing a little bit away from you Now it is very important to differentiate between specular reflection and diffuse reflection, because: ![]() Specular reflection (mirror or shiny surface), this is elastic scatteringĭiffuse reflection, (not mirror, faded), this is absorption, and re-emission ![]() In your case, the visible light we see from an object is mostly from its surface, there are two cases for visible light coming from the surface of the object: Now there are visible and non-visible wavelength photons, but in your case, only the visible ones are more important, so I am going to talk about those (except for absorption and re-emission in which case the absorbed non-visible light might be re-emitted partly as visible wavelength light). Inelasstic scattering, the photon gives part of its energy to the atom and changes angleĪbsorption, the photon gives all its energy to the atom and electron When a photon interacts with an atom, three things can happen:Įlastic scattering, the photon keeps its energy and changes angle
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