Why do darker materials heat up more than lighter ones if light

Brainlet here, I would think because the darker material absorbs a wider spectrum of light and therefore literally more energy

>emission is proportional to light absorption

It is not, youre incorrect on that portionz. Blackbody radiation and energy absorption are two different things. And they are very loosely related but specifically not how you described.

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>>8830405
>tfw you took the convection heat transfer graduate class instead of the radiation one

>>8830405
>Shouldn't they have the same net increate in temperature?
Since they pretty easily observably don't have the same net, then might it be worth readdressing your ideas on how this works?

>>8830427
>>8830415

I'm being told that a perfect blackbody will rapidly reach thermal equilibrium because its both an idea emitter and an idea absorber. This makes sense to me since it's just the same process in reverse but then why do dark objects get hot at all. Is it just that they are measured to be hotter without being hotter because they're emitting all the heat they absorb?

>>8830429
Because there is no such thing as a perfect blackbody. Things in real life dont emit exactly the amount of energy they release, just doesnt exist. Look up black body radiation. It is an unrealistic perfect case example to help understand the theory, nothing more.

>>8830429
The peak energy emittance is proportional to T^4, so it will reach thermal equilibrium because as temperature raises, emittance raises much faster and eventually the body would start cooling down, but then the emittance would also be lower, and this is the point it reaches equilibrium. Maybe that's what you are talking about.

As for why a body absorbs certain wavelengths but doesn't emit them, got no idea.

>>8830442
dude, why do you even bother posting if all you do is shit on science for being unrealistic? Don't you have a bible study group to go to?

>>8830447
so suppose I had a perfectly black paint and I sprayed it on a ball at room temp and then left it on the window sill. What would happen?

>>8830452
It would get hot, but peak emittance wouldn't go beyond infrared, so you wouldn't notice it glowing, even though it would be. Put it in an oven, though, and you would quickly see it getting red, orange, yellow and white, just like metal in the fire.

>>8830453
so how hot would it actually get?

>>8830460
Exactly the temperature of the oven. Or else it wouldn't be in thermal equilibrium.

>>8830462
In that case what about a perfect whitebody? Would it be unable to lose heat?

>>8830405
>Why do darker materials heat up more than lighter ones if light emission is proportional to light absorption?
Emissivity is wavelength-dependent. Many substances with high reflectivity and low absorption of visible light will have drastically different properties at thermal wavelengths. So when sunlight (~600 nm) hits snow, only 13% of that energy is absorbed with the rest reflected, but at longer thermal infrared wavelengths (~10,000 nm), snow radiates (and absorbs) readily with 82% emissivity. Expose that same snow to longwave thermal infrared radiation, INSTEAD of visible light, and it will absorb THAT radiation much more readily.

Black surfaces have similar thermal emissivities to white ones, but they get hotter under visible-light irradiation because their absorptivity of VISIBLE wavelengths is higher and albedo is lower.

http://www.solarmirror.com/fom/fom-serve/cache/43.html

Put a white and a black object out in the sun, and I'm pretty sure the energy they're absorbing dwarfs anything they're emitting.

>>8832470
Only until their temperatures equalize with input/output based on energy input and environmental factors. Object only have so much thermal mass.

>>8832470 here.
Did rough calculations, that was wrong and dumb. Disregard it.