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Author Topic: Do certain colors (besides black and white) get hotter faster?  (Read 6360 times)

Offline JasmineRain

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I know that white reflects all the colors of the rainbow and black absorbs them all, and that if something is a certain color like green it means its absorbing every color except it's color (green), which it's reflecting, but do different colors hold more energy? Like, would something that was blue be hotter than something that was yellow, or are all the colors the same temperature?


 

Offline litespeed

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Energy contained in electromagnetic radiation increases as the frequency increases. Accordingly blue light carries more energy then yellow light. Stipulating full reflection of blue as well as full absorbtion of yellow, subsequent heat capture would be less in this case then if the reverse were true.

I have no idea, however, how much percentage difference one color is over another. Here is a chart of the electromagnetic spectrum. http://www.antonine-education.co.uk/physics_gcse/Unit_1/Topic_5/em_spectrum.jpg
 

Offline yor_on

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No, you're right. and you know it too :)

Walk on asphalt and then on the grass barefoot.
Which one do you prefer, why?

The grass is cooler than the dark asphalt, right? What is the colors you see when you look at that grass? Mostly greens right? that's the only wavelengths that grass let out, the rest it keeps, more or less. The asphalt, if it's a pure black, takes in all wavelengths, absorbs them and transform them into heat (infra red radiation). And different colors do this to different degrees with pure black being an total absorption potentially. Heat is a description of movement, like inside a molecule 'vibrating'.

It contains a certain energy that, if transformed into infrared, will become heat. Those molecules can bump into something transferring this 'heat/energy' in form of kinetic energy to each other(Conduction) and also a amount of infrared radiation to the atmosphere . They can also raise up in the atmosphere (convection) taking the heat with them to lose it ultimately to space.

And then finally you have radiation like from a light bulb that radiates heat amongst all other wavelengths it gives out. So the lighter you find a material to be, the less heat it should contain. I haven't seen any real definition of how color compare to heat normally in nature, maybe there is one, somewhere?

One thing that may confuse the matter is that when looking at f.ex stars those that seems 'bluish white' will be hotter than those that are 'Yellow red'. But that is the radiation let out from them, not the radiation absorbed. Color temperature
==

Hmm, rereading you, you do ask about what color is the hottest don't you :)

Well, look at the link i gave for that, it answers your question. But that hasn't to do with absorption, it has to do with the wavelength/frequency of the wave you observe, and there blue, or white, will be hotter than red. You have also to remember that the eye can't see all wavelengths there are. Take a look here for the high energy, visible spectrum and the visible spectrum.
« Last Edit: 18/04/2010 23:06:33 by yor_on »
 

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