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I know there are a Wien's law for frequency and one for wavelenght, but I'm wondering which one is the most accurate when it comes to our perception of colors. For instance for the Sun, the Plank function in wavelenght has a peak at 499nm, so green; but the one in frequency has a peak at 339Thz, so in near IR;
people always say the peak is in the green for the Sun, but why not use the "Wien's law in frequency" instead? Does it mean our eyes are "wavelenght spectrometer"?
I guess the Sun is a bad example since it appears white anyway, but one could ask the same about other black bodies like hot metal

Thanks

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  • $\begingroup$ If you look at Wikipedia the point is addressed. Basically it is due to the different shape of the distribution, but radiance under the distribution stays the same when integration is between two wl or their corresponding frequency. $\endgroup$
    – Alchimista
    Commented Apr 15, 2021 at 9:49
  • $\begingroup$ yes I am aware of that difference, but what I am wondering is which law (in frequency or wavelenght) describes our human perception best $\endgroup$
    – Bilzebor
    Commented Apr 15, 2021 at 21:23
  • $\begingroup$ @Bilzebor there are many many questions and answers about human color perception here in physics stackexchange. Blackbody radiation has no part in it. Alchimista's answer is very accurate in terms of the physical reality of blackbody radiation, I think your problem is in understanding what a distribution of light radiation really means. Both laws represent exactly the same spectrum, one in $d\nu$ the other in $d\lambda$, and both have nothing to do with human perception of color. $\endgroup$
    – José Andrade
    Commented Apr 16, 2021 at 14:45
  • $\begingroup$ Let me put it in a kind of different, maybe not super accurate, analogy. By touching a piece of rubber or of copper, both at 60°C, for 1 second, for copper I will burn myself, rubber, it just feels warm. Still both are at 60°C and from there I cannot draw any conclusions about human touch. A very crude assumption would tell you that the rubber has a lower temperature because it did not burn you, but their physical temperature was the same. Blackbody radiation has a spectrum, can be expressed in wavelength or frequency, but human perception is a biological way to perceive the world around us $\endgroup$
    – José Andrade
    Commented Apr 16, 2021 at 14:54
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    $\begingroup$ yes the blackbody radiation was maybe not the best idea for an example, but my question remains: the maximum of a spectral distribution isn't the same for a frequency distribution (something in power/Hz) and wavelenght distribution (in power/m), so which maximum is the right one for our eyes? It can't be both, since they're not the same (with the example of the Sun, I get either green of near infra-red depending on which law I use). Sorry if I'm not clear enough but thanks for your answer! $\endgroup$
    – Bilzebor
    Commented Apr 19, 2021 at 18:21

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