December 14, 2014 at 9:12AM


Isn't it strange referring to blue light as the "cooler" light when its color temperature is hotter than red light, which we ironically call the "hotter" light?

Although the color temperature is not the operating temperature of light, it does have a positive correlation with heat.

So, a bluer light is actually hotter and thus has a higher kelvin value than a redder light, which has a lower kelvin temperature value, and also thus produces lesser heat, and must be cooler than the blue one.

However, we call them the opposite names. We call a blue light a cooler light and a redder light, we call the warmer light. Why is that?


I got the answer to my question while reading the Wikipedia entry on Color temperature.

Here's the relevant excerpt that answers the question:

Color temperatures over 5,000K are called cool colors (bluish white), while lower color temperatures (2,700–3,000 K) are called warm colors (yellowish white through red).[1] This relation, however, is a psychological one in contrast to the physical relation implied by Wien's displacement law, according to which the spectral peak is shifted towards shorter wavelengths (resulting in a more blueish white) for higher temperatures.


In layman terms, we call them so for the psychological association we have of blue being cool and yellow being hot.

December 14, 2014 at 11:49AM


I've often wondered the same thing...

February 17, 2015 at 6:11PM, Edited February 17, 6:11PM


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