Hi, this is a hot topic !
a wavelength actually is a length (as you could derive from the name).
Ok, they're real short distances, so small that even a centimeter (cm) is an
almost galactic distance in comparison, that's why it's measured in um wich
stands for micrometers.
This measures the length it takes for a wave to accomplish a full cycle. The
shorter this distance, the higher the frequency.
The waves are similar to the waves that ripple when you throw a stone in
water.
But, in the case of heat, the stones are the atoms jumping around because of
excitement. And as everyone can witness, even a very tiny and charming
thing, when excited may pertubate the environmnent.
Basically, when an atom is very excited, you can see it. I mean it's
luminous ..., you can see it's excited because the frequency of the
perturbation is so high that it makes light. Easy : if it's very excited, it
jumps very fast, I mean frantically, at great speed, so the wavelength is
short : it's light.
If it's midly excited, it isn't so fast and the light color becomes reddish
... just like, what one could say : a warmer color ... is the atom cools
down, then it may even become infra - red. As a matter of fact it becomes a
really warmer color, it even may become only warmness with almost no color
at all (at least none that your eye can see).
That's the reason why, even if your barbeque or oven is not flaming red, you
may become very excited when touching it. Even if the atom isn't this much
excited it's able to communicate it's excitement : that's propagation.
To resume : the higher you get excited when touching your oven, the higher
the frequency, and the lower the wavelength. And if you're screaming, it's
because your finger is a good heat detector. Some satellites or cameras are
even better heat detectors, and that's the reason why they often need to be
refrigerated, just like your finger.
Hope it helps.
> -----Message d'origine-----
> De : [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]De la part de
> [EMAIL PROTECTED]
> Envoye : mardi 15 mai 2001 17:54
> A : [EMAIL PROTECTED]
> Objet : MI-L MI - um symbol
>
>
> Listers,
> I'm attempting to map wavelength data (of which I know nothing) and keep
> coming into the notation "um" where the u is really the Greek mu. Nobody
> here at our office knows what this means or what it is. We're not
> engineers.
> If it helps, the data are thermal images tied to ground truths.
> Can anyone
> tell mell what unit of measure "um" is? Further, what does it
> mean? How is
> it used? What does it describe?
> Thanks for your patience
> Scott
>
>
>
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