Light: Reflection, Re-emission, or both?

In summary, when discussing the colors of objects and the reflection of light, it is believed that some pigments absorb light while the reflected light represents the color that is seen. It is still unclear if the light is actually reflected or if it is just absorbed and emitted again. Evidence suggests that there are two types of reflections occurring, one due to the outermost electrons and the other due to electron energy-levels. It is difficult to determine if the reflected light is the same photon or a replica, as a photon can replicate itself continuously as it travels through space.
  • #1
Dissident Dan
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2
In basic science class, when talking about light and the colors of objects, people will say that the pigments absorb some light, but the light that represents the color you see is reflected.

Is light actually reflected (the same photons/waves still exist and are now traveling in a different direction as a result of the interaction with the material), or are they merely absorbed and new light is emitted by the material? Maybe a little of both?
 
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  • #2
Take a smooth, flat, black object, something like obsidian or polished marble, or a very glossy painted surface (I'm looking at a painted metal disk). You will notice that, to some extent, there will be some specular reflection (like a mirror)that will still have the color of the thing that is reflected. Yet the thing is still "black" which means it's supposed to absorb all light that hits it.

This is some evidence that indicates two kinds of reflections going on. The specular reflection is not an "electron energy-level" absorbtion reemission; instead it is reflection due to the outermost electrons which are loosely bound to the nucleus and can reflect any wavelength of light.

THe color is still black because most of the light that falls on the surface is still absorbed. IF you are looking at a blue object, most of the blue light that you see is being absorbed and reemiited back at you, but some of all wavelengths of light will still be reflected by those outer electrons. So depending on the surface material, a bit of both will occur.

I don't think that you can say for either type of reflection it is the "same photon" in the sense that it's the same tennis ball that you hit back to your opponent. But also, you can't say that it's a different photon either; if it has exactly the same wavelength, then it is the same package of energy coming out as the package of energy that went in. A philosophical point, I think.
 
  • #3
Thanks for the response.

However, I don't quite get the last response, and it's related to what I was wondering about. It it the actual same physical entity that is now moving in a different direction, or is it a replica?
 
  • #4
Originally posted by Dissident Dan
Thanks for the response.

However, I don't quite get the last response, and it's related to what I was wondering about. It it the actual same physical entity that is now moving in a different direction, or is it a replica?

Tricky question. A photon essentially replicates itself continuously as it propagates through space (through electromagnetic induction). We have a problem in defining what actually is the entitiy that is a photon. At the root of it all, the photon is a package of energy that exists as an electric and magnetic field "undulation." IT behaves sometimes like a particle, but not enough to liken it to a tennis ball.

WHen a photon is absorbed, the energy is momentarily contained by an excited electron. At this point there is no photon. THen the energy is released by the electron and with this de-excitation, a photon is created. So since there was no photon at some point, you could argue that a different photon was created.

Various things could happen that would make some of the properties of the photon different : it's polarization could shift, its direction of propagation could change (refraction or scattering), and these could be reasons to call it a different photon.

I believe that reflection from a metallic surface would also cause there to be an instant where there would be no photon, so this form would be in the same boat. THe big difference is that metallic reflection does not cause polarization of reflected light.

But then, I just repeat: if it's teh same energy package, who's to say it's not the same photon?
 

What is light?

Light is a form of electromagnetic radiation that is visible to the human eye and is responsible for our sense of sight. It is made up of tiny packets of energy called photons and travels in a straight line at a very high speed.

What is reflection?

Reflection is the bouncing back of light when it hits a surface. This can happen with a smooth surface, such as a mirror, or with a rough surface, where the light is scattered in different directions.

What is re-emission?

Re-emission is the process by which an object absorbs light and then emits it back out in a different direction. This can happen with all types of light, including visible light, infrared, and ultraviolet.

How is light reflected?

Light is reflected when it hits a surface at a specific angle, called the angle of incidence. The angle of incidence is equal to the angle of reflection, which means that the light bounces off the surface at the same angle it came in at.

Can light be both reflected and re-emitted?

Yes, light can be both reflected and re-emitted. When light hits a surface, some of it may be reflected, while the rest is absorbed and then re-emitted in a different direction. This is known as diffuse reflection and is the reason why we can see objects that are not directly in the path of the light source.

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