# Reflection and absorption in matte black vs. shiny black objects

• rolaluv
In summary: The index of refraction and the angle of incidence determine the reflectance. Metals have a high index of refraction, and so are shinier.How rough or smooth a surface is determines if it looks mirror like or matt. How absorptive a material is determines how much light goes out the other side, not how much reflects. However, it does seem that a white car reflects more light than a black one, so I'm not completely sure about this.As for quantumly, light raises electrons, which then fall back down and release the light. Why it goes one direction instead of another I don't know. I would think it would scatter, though it does not. But I
rolaluv
Hi,

I'm confused about reflection and absorption in materials. Is glossiness of an object determined by roughness of its surface rather than its inability to absorb visible light?

If there are dark-colored objects where one has a matte finish and the other has a glossy finish, does this mean that reflections at these surfaces (which are due to differences in refractive indices in the ray optics model) are diffuse vs. specular? In other words, will objects appear shiny if the surface is smooth and undergoes specular reflections and appear matte if reflection is diffuse?

I don't think the reflections at the surface which determines the texture of a material (shiny or matte) is due to absorption-- because if a dark object absorbs most of the incoming light, then it shouldn't reflect any light back and have a matte finish, right? So I thought every surface has some reflections because it has a different index of refraction than air, and its texture is determined by the roughness of the surface.

Am I completely mistaken on this?

Also, what is the quantum explanation of reflection?

One more point-- if my understanding of reflection is right, why are matte black objects better emitters/absorbers than shiny black objects? This contradicts my assumption where both objects absorb and reflect, but one reflects diffusely and the other reflects specularly.

Last edited:
The index of refraction and the angle of incidence determine the reflectance. Metals have a high index of refraction, and so are shinier.

How rough or smooth a surface is determines if it looks mirror like or matt.

How absorptive a material is determines how much light goes out the other side, not how much reflects. However, it does seem that a white car reflects more light than a black one, so I'm not completely sure about this.

As for quantumly, light raises electrons, which then fall back down and release the light. Why it goes one direction instead of another I don't know. I would think it would scatter, though it does not. But I guess depending on the frequency, the more time the photon spends on the electron, giving the dispersion we see in prisms. I doubt the speed of light in between electrons is any different for any materials, though I have heard of some materials having an index less than 1, which I guess would contradict that.

Stargazer19385 said:
The index of refraction and the angle of incidence determine the reflectance. Metals have a high index of refraction, and so are shinier.

How rough or smooth a surface is determines if it looks mirror like or matt.

How absorptive a material is determines how much light goes out the other side, not how much reflects. However, it does seem that a white car reflects more light than a black one, so I'm not completely sure about this.

As for quantumly, light raises electrons, which then fall back down and release the light. Why it goes one direction instead of another I don't know. I would think it would scatter, though it does not. But I guess depending on the frequency, the more time the photon spends on the electron, giving the dispersion we see in prisms. I doubt the speed of light in between electrons is any different for any materials, though I have heard of some materials having an index less than 1, which I guess would contradict that.

Be careful here, because the way light interacts with solid surfaces is not as simple as the way photons interact with single atoms (what we are all taught to start with). If it were as simple as that, there would be no specular reflections and all you would get would be scattering due to absorption and random re-emission.

Stargazer19385 said:
How absorptive a material is determines how much light goes out the other side, not how much reflects. However, it does seem that a white car reflects more light than a black one, so I'm not completely sure about this.
A white car does reflect more light than a black one.

Car paints use a clear binder that contains suspended pigment particles (and I think there is a clear coat on top as well). There is some specular reflection from the binder regardless of the color of the pigment; this produces the "gloss". Light that is not reflected from the binder strikes a pigment particle. If the pigment is white, the light is likely to be reflected; after some number of reflections, the light will emerge in an essentially random direction. If the particle is black, the light is likely to be absorbed.

rolaluv said:
Hi,

I'm confused about reflection and absorption in materials. Is glossiness of an object determined by roughness of its surface rather than its inability to absorb visible light?

If there are dark-colored objects where one has a matte finish and the other has a glossy finish, does this mean that reflections at these surfaces (which are due to differences in refractive indices in the ray optics model) are diffuse vs. specular? In other words, will objects appear shiny if the surface is smooth and undergoes specular reflections and appear matte if reflection is diffuse?

<snip>

Yes- 'gloss', or other appearance effects (haze, color-shifting finishes, etc) are due to surface properties, not bulk properties (of which absorption is one).

Modeling rough surface reflections can be done with ray-optics, but in general it is tedious and requires a microscopic description of the surface shape. Other models (Torrence and Sparrow, Oren-Nayar, etc.) are usually based on radiometry and use the BRDF (http://en.wikipedia.org/wiki/BRDF) to describe how light is scattered from the surface.

## 1. What is reflection and absorption in objects?

Reflection and absorption are two processes that describe how an object interacts with light. Reflection occurs when light bounces off the surface of an object, while absorption occurs when light is taken in and converted into heat energy by the object.

## 2. How does the surface texture affect reflection and absorption in black objects?

The surface texture of an object can greatly affect its reflection and absorption properties. Matte black objects have a rough surface, which can scatter light and decrease reflection. Shiny black objects have a smooth surface, which can reflect light more efficiently.

## 3. Why do matte black objects appear darker than shiny black objects?

The difference in appearance between matte black and shiny black objects is due to the amount of light that is reflected. Matte black objects reflect less light and absorb more, making them appear darker. Shiny black objects reflect more light, giving them a brighter appearance.

## 4. Which type of black object is better at absorbing heat?

Matte black objects are better at absorbing heat because they have a larger surface area for absorption and are not as reflective as shiny black objects. This is why matte black surfaces are often used for heat sinks and other applications where heat transfer is important.

## 5. Can reflection and absorption properties be changed in black objects?

Yes, the reflection and absorption properties of black objects can be altered by changing the surface texture or by applying coatings or treatments. For example, a shiny black object can be made to appear matte by adding a rough surface texture, and vice versa.

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