Understanding Light Reflection and Black Bodies in Nature

In summary, there are two types of light reflection: specular and diffuse. Specular reflection is when light is absorbed and re-emitted by an electron cloud, creating micro currents that produce nearly identical photons to the incident ones. In diffuse reflection, light is emitted in a random direction based on the dominant path back to lower energy levels. The color of a surface is determined by this path. The concept of a black body absorbing all wavelengths but also dissipating them can be explained by the fact that a black body radiates with a black body spectrum at nonzero temperature. However, this does not make it appear black. The question of whether light is actually reflected or new light is created is not fully answered in quantum mechanical theory, as photons are ind
  • #1
TurdMuppet
One thing that has allways disturbed my mind is the correct understanding of lightinteractions in nature.

When we're talking about light reflection (light that is reflected in an arbitrary direction, not like mirrors) is it really reflections or is it new light created by the incoming light that stimulates the material. One other example of this are the flourocerent colors which means that the dissipating wavelength is different that the incoming ones. In this case it must be that the light isn't really reflected but created (and sent out in an arbitrary direction) in the material when light is lit on it. Can anyone please give me a good physically correct answer for this.

Another thing is the confusion with "black bodies". According to physics the black body should absorb all wavelengths but it should also dissipate all wavelengths. Then how can the body be black? Confusing contradiction.
 
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  • #2
Your question is rather vague so I just give you some general information. First find a copy of GED by Richard Feynman, it is a good layman explanation of the fundamental processed which govern what we see.


There are 2 general types of reflection, specular and diffuse. Specular is what a mirror does, diffuse is what a painted wall does. ALL light is adsorbed and re-emitted by the surface it strikes. Specular reflections are generally generated by conducting surfaces, at the atomic level these surfaces consist of what is called an electron gas. This means that there is a huge number of available energy levels, photons in the visible spectrum interact in a nearly continues fashion, thus creating micro currents which re-emit photons nearly identical to the incident ones.

In a diffuse reflection the atoms which adsorb the incident photons reemit them in a random direction. The incident photons arrive in a range of energy ranges which excite the atoms to a range of electronic energy levels, upon relaxation there will be a dominate path back to the lower energy levels, this path will determine the color of the surface.


Please repost your black hole question to the cosmology forum.
 
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  • #3
Originally posted by TurdMuppet
According to physics the black body should absorb all wavelengths but it should also dissipate all wavelengths. Then how can the body be black?

Any blackbody at nonzero temperature will radiate with a blackbody spectrum, so it will not look black. It's called a blackbody because the light it radiates is independent of the spectrum of light incident on it: it's not reflected light.

Originally posted by Integral
Please repost your black hole question to the cosmology forum.

It wasn't a black hole question.
 
  • #4
Originally posted by Integral
Your question is rather vague so I just give you some general information. First find a copy of GED by Richard Feynman, it is a good layman explanation of the fundamental processed which govern what we see.


There are 2 general types of reflection, specular and diffuse. Specular is what a mirror does, diffuse is what a painted wall does. ALL light is adsorbed and re-emitted by the surface it strikes. Specular reflections are generally generated by conducting surfaces, at the atomic level these surfaces consist of what is called an electron gas. This means that there is a huge number of available energy levels, photons in the visible spectrum interact in a nearly continues fashion, thus creating micro currents which re-emit photons nearly identical to the incident ones.

In a diffuse reflection the atoms which adsorb the incident photons reemit them in a random direction. The incident photons arrive in a range of energy ranges which excite the atoms to a range of electronic energy levels, upon relaxation there will be a dominate path back to the lower energy levels, this path will determine the color of the surface.


Please repost your black hole question to the cosmology forum.

Thanks for the answer. In the case of specular reflection I think you said that the light is actually absorbed and then reemitted by the electron cloud. I can understand in the diffuse case when light is emitted in a random fashion. In specular case, what makes the light reflect then so that the law of reflection really occurs if the light is really absorbed?

You talk about two cases, diffuse and specular. Are those types of reflections really two completely different cases. You often see materials that are both, meaning that they are somewhat diffuse and somewhat shiny like a mirror. How can a material be both?
 
  • #5
Originally posted by TurdMuppet
... is it really reflections or is it new light created by the incoming light that stimulates the material...

This is an example of a question which has no sensible answer in quantum mechanical theory. Photons are indistinguishable particles; there is no way to label them, so there is no way to test whether a given light ray emanating from the mirror is the same one which was launched. Look up "indistinguishability" together with "quantum mechanics".
 

What is light reflection?

Light reflection is the process by which light bounces off a surface and changes direction. This occurs when light rays hit a smooth surface and are reflected in a predictable manner, known as the law of reflection.

Why do objects appear different colors?

Objects appear different colors because of how they reflect light. Objects that appear red absorb all colors of light except red, which is reflected back to our eyes. Objects that appear white reflect all colors of light, while objects that appear black absorb all colors of light.

What is a black body in nature?

A black body in nature is an object that absorbs all wavelengths of light that hit it, making it appear black. It is considered an ideal absorber and emitter of light, and its temperature determines the color of light it emits.

How does light reflection affect plant growth?

Light reflection plays a crucial role in plant growth as plants use light for photosynthesis. Different wavelengths of light are reflected off plants, which can affect their growth and development. For example, blue light is necessary for photosynthesis and red light is important for flowering.

What is the relationship between light reflection and climate change?

Light reflection and climate change are closely related as the reflection of light can affect the Earth's temperature. When light is reflected off the Earth's surface, it can either be absorbed by the atmosphere, leading to an increase in temperature, or reflected back into space, cooling the Earth. Changes in the Earth's surface, such as melting ice or deforestation, can impact light reflection and contribute to climate change.

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