This may be a stupid question, but I've been wondering this for a while and haven't yet found a solid answer. I'm worried the answer will be something along the lines of "of course not, you dummy" but it's bothering me and I haven't found the answer so I figured I'd take the risk. Is it possible for matter to ONLY be visible in an area of the spectrum other than visible light? For instance, can any matter be invisible to us but visible in the UV or IR range?

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    $\begingroup$ 'Visible' is a very subjective term here. Do you mean it's dim enough in one wavelength that it is not visible for a certain instrument? Or does visible mean that there is zero emission at that wavelength? The point being, there is almost never zero emission at any wavelength, and whether something is visible or not depends on the instrument limits or other brightness characteristics. For example, a blackbody spectrum emitting body like a human may be visible to an instrument at its peak emission wavelengths (say IR) and not visible at other wavelengths (like visible light). $\endgroup$
    – Takku
    Jul 1 '14 at 20:58

While individual atoms or molecules can emit energy at discrete or narrow ranges of wavelengths, once you have larger chunks of matter (and they are above absolute zero) they will emit, at least, a continuous black body spectrum. While black body radiation can be observed at all wavelengths, far away from the peak wavelength it may be below our ability to detect its emission.

  • $\begingroup$ Thank you for the response. I remember the term "black body" from a class I once had, but I didn't find it in my searches for this question. I'll start reading up on that again. Thank you. $\endgroup$
    – duzzy
    Jul 6 '14 at 17:13

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