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teddoman
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A blackbody radiator emits radiation across the entire radiation spectrum. The "temperature" of the blackbody radiator (measured in kelvin) can be directly calculated from the peak wavelength of its radiation using Wien's[/PLAIN] displacement law.
At shorter wavelengths, the temperature is higher.
Most objects, even stars, are not actually blackbody radiators as predicted in theory, for various reasons. A spectrum of radiation that is not a true blackbody radiator is not described by its actual temperture but by its correlated color temperature (CCT) essentially by the closest blackbody radiator's temperature.
My question is in regards to natural daylight which apparently can reach 25,000 kelvin. This is in contrast to the actual temperature of the surface of the sun which is closer to 5,800 kelvin. A high CCT implies the peak wavelength is shorter. I have read unconfirmed assertions that a cloudy day or morning might be closer to 5,800 while a clear bright day might reach a much higher CCT like 25,000.
I have read about Rayleigh scattering and other atmospheric effects, but I haven't been able to find resources specifically about the direct impact of these effects on the radiation spectrum of daylight. One person asserted to me that clouds filter out longer wavelengths, but this would imply the highest CCT of daylight is on cloudy days, not sunny days.
I tried searching in the astrophysics and Earth forums, and I found some tangential threads but nothing directly addressing this. I am not a physicist and my interest in this question arises from photography. Can anyone here explain, or point me to a resource that explains, the mechanics of how the radiation spectrum of daylight can sometimes be at very short wavelengths (and hence have a very high correlated color temperature)?
At shorter wavelengths, the temperature is higher.
Most objects, even stars, are not actually blackbody radiators as predicted in theory, for various reasons. A spectrum of radiation that is not a true blackbody radiator is not described by its actual temperture but by its correlated color temperature (CCT) essentially by the closest blackbody radiator's temperature.
My question is in regards to natural daylight which apparently can reach 25,000 kelvin. This is in contrast to the actual temperature of the surface of the sun which is closer to 5,800 kelvin. A high CCT implies the peak wavelength is shorter. I have read unconfirmed assertions that a cloudy day or morning might be closer to 5,800 while a clear bright day might reach a much higher CCT like 25,000.
I have read about Rayleigh scattering and other atmospheric effects, but I haven't been able to find resources specifically about the direct impact of these effects on the radiation spectrum of daylight. One person asserted to me that clouds filter out longer wavelengths, but this would imply the highest CCT of daylight is on cloudy days, not sunny days.
I tried searching in the astrophysics and Earth forums, and I found some tangential threads but nothing directly addressing this. I am not a physicist and my interest in this question arises from photography. Can anyone here explain, or point me to a resource that explains, the mechanics of how the radiation spectrum of daylight can sometimes be at very short wavelengths (and hence have a very high correlated color temperature)?
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