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Physicsissuef
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Why the black objects absorb more light and heat from the other color objects?
What is the structure of the black color?
What is the structure of the black color?
Without complicating the matter too much:Physicsissuef said:Why the black objects absorb more light and heat from the other color objects?
What is the structure of the black color?
Andy Resnick said:Hang on... just because and object is black (highly absorptive) in the visible just not mean it is also black in the infrared. Snow is black in the IR region, for example.
How efficient an absorber a dielectric (or any material) is depends on both microscopic bulk properties (atomic/molecular absorption) but also on surface structure- textured surfaces can appear black under some conditions.
DaveC426913 said:Without complicating the matter too much:
Black objects are black because almost all the light that falls on them is absorbed into the material. Little or no light is reflected back toward your eye, therefore you see black. That light that is absorbed ultmately becomes heat.
White objects are white because almost all the light that falls on them is reflected by the material. Because all the light is reflected back toward you eye, you see white. Little light is turned into heat.
Red objects absorb light at frequencies other than red and tend to reflect frequencies near red. They don't get as warm as objects that are black.
The nature of an object's colour has to do with the molecules and their electrons. Electrons in different states absorb different frequencies. When we build things - and especially when we paint them - we choose materials that contain molecules with very specific reflection frequencies. For example, Phthalo green - a paint colour - has very stable molecules in it that reflect light in a very specific, predictable band of green. Lamp black - another paint colour, has molecules that absorb ALL frequencies of light.
Too simplistic and misleading.jobyts said:Is it correct to say, white objects do nothing with the incident EM waves, and black objects change the frequency (to IR range)?
DaleSpam said:What always surprises me when I think about these kinds of things is shiny black objects! How weird. They reflect a lot of light (specular reflection), but they are black (diffuse absorption). Definitely a "surface structure" effect as mentioned above, but still interesting.
DaveC426913 said:Kinetic energy = heat so the object is slightly warmer.
Andy Resnick said:Hang on... just because and object is black (highly absorptive) in the visible just not mean it is also black in the infrared. Snow is black in the IR region, for example.
That's what heat is.jobyts said:Why is kinetic energy == heat , for every substance?
jobyts said:I was wondering how would any substance can be black for the infrared. If a substance reflects all the infrared rays, it should be white for the IR rays. If it absorbs the IR rays, it would cause the lattice to giggle, and emit heat, which is again in IR. So in any case, it should emit IR, right?
DaveC426913 said:That's what heat is.
DaveC426913 said:That's what heat is.
Physicsissuef said:do the black body release the energy, that it absorbs?
If you polish a black rock you can turn a dull black rock into a shiny black rock. I suppose that it is possible that the polishing process adds a "coating" but I thought it just rubbed pieces of rock off until the resulting stone was smooth.dst said:Is that caused by a transparent & reflective layer on top of the black layer? An example would be anodized aluminium or powdercoating on, well anything. What raw material can actually do both without any change in composition?
Physicsissuef said:Why the black objects absorb more light and heat from the other color objects?
What is the structure of the black color?
DaleSpam said:If you polish a black rock you can turn a dull black rock into a shiny black rock. I suppose that it is possible that the polishing process adds a "coating" but I thought it just rubbed pieces of rock off until the resulting stone was smooth.
I think a very small portion of the absorbed energy is released.jambaugh said:Yes but before it can be released it usually gets spread about in the kinetic energy spectrum (something called equipartition of energy) so that when visible light hits the black body it is re-released as infrared radiation in a thermal spectrum.
jobyts said:Let me be clear on some basics. Please correct if I am wrong.
Energy is a measure on the ability to do work on matter. Matter can do work on other matter, which is kinetic energy (eg; a moving object). EM wave can do work on matter, hence they have energy too. Heat is a just IR wave in the EM spectra.
jobyts said:In my understanding, the connection between EM wave to kinetic energy comes as follows:
An EM wave hits an atom; cause it to do work on the atom (causing the electrons to move; EM energy to kinetic energy conversion). Then the electron emits another EM energy which is Infrared ray, which we call heat.
My question is what property of the matter/electron caused it to emit waves in the IR frequency. Why not in some other frequency?
Physicsissuef said:I think a very small portion of the absorbed energy is released.
DaveC426913 said:As the person who spurred the "what is heat" sub-discussion, I'd like to ask that we return to the OP's question. I think the answers are getting a little too academic to really be helping the OP. So:
"Why is kinetic energy == heat , for every substance?"
Black objects absorb more light and heat because they contain a higher concentration of pigments that are able to absorb a wider range of light wavelengths. This means that they are able to absorb more energy from the light that hits them, resulting in a higher temperature.
No, not all black objects absorb more light and heat. The absorption of light and heat depends on the material and pigments used to make the object. Some black objects, such as those made of reflective materials like metal, may actually reflect more light and heat.
The color of an object is determined by the wavelengths of light that it reflects or absorbs. Black objects reflect very little light and absorb most of the light that hits them, resulting in higher heat absorption. In contrast, lighter colored objects reflect more light and absorb less heat.
Yes, the temperature of a black object can be affected by the color of the light source. Black objects are better at absorbing light in the visible spectrum, so they will absorb more heat from a light source that emits visible light. However, they may not absorb as much heat from a light source that emits infrared light.
The absorption of light and heat by black objects, such as asphalt and buildings, can contribute to the urban heat island effect. This is when cities experience higher temperatures due to the absorption of heat by dark surfaces. It can also contribute to global warming, as black objects absorb more heat from the sun, leading to an increase in temperature over time.