weird_alice - 21-10-2017 at 00:23
Used for that or called that way.
Why is not ultraviolet, isn't it of higher energy?
If UV is not heating, then where does the energy go? Reflected to somewhere? Passes trough something?
Sulaiman - 21-10-2017 at 01:19
I think that infrared light is associated with heating mainly because it is relatively easy to produce a lot of infrared energy with common materials,
to produce ultraviolet needs temperatures well above the melting points of most engineering materials,
or more usually emission from exited gasses, usually mercury for uv.
A many kW uv lamp is very much more expensive than electrically heated wires etc.
and, a uv lamp of several kW would blind people really quickly, create lots of toxic reactive ozone, kill all cellular life .......
but it could be used as a heater.
metalresearcher - 21-10-2017 at 02:24
Current LEDs however can produce UV light as well. There are even dedicated low power 'blackleds' i.e. a blacklight LED in a low power torch. But they
produce barely heat.
In stars, the hotter the star (spectral class O, B or A), the more energy it delivers per kilogram of material.
If our Sun were 10000K (more blue light and less infrared) instead of 5800K, the Earth would be scorched away and life would not be possible.
unionised - 21-10-2017 at 02:40
At least part of the distinction might be because IR heats things, but doesn't generally cause other changes.
Visible and UV light produce photochemical changes (in some materials) which are different from those caused by simple heating.
barbs09 - 21-10-2017 at 04:17
Hi, I will probably be corrected, but different things adsorb different wave lengths differently. We being mainly water adsorb the IR spectrum
efficiently. Whereas longer wave lengths such as radio waves or shorter wave lengths such as X-rays/ gamma rays and not readily adsorbed by our tissue
and we are effectively rendered transparent to them.
Obviously our cells are not completely transparent to very short wave radiation, otherwise it would pose no risk.
vmelkon - 21-10-2017 at 16:57
I agree with the above answers. It is very difficult to produce large quantities of blue, indigo, violet, UV light if you are going to do it by
heating a material. You get that blackbody style graph. Most of the emission is in the IR.
You could buy a UV laser.
Example:
http://www.cnilaser.com/UV-Laser-257nm.htm
This is 1 to 15 mW which is nothing.
A violet blue laser
http://www.cnilaser.com/blue_laser400.htm
It is 300 mW.
That should be enough to burn holes in some black PVC tape.
https://www.amazing1.com/products/355nm-ultraviolet-laser-mp...
355nm Ultraviolet Laser MPL-W-355 Solid State 100-800mw Pulsed
Twospoons - 21-10-2017 at 20:41
All light is 'heating', if it gets absorbed. In fact I'd broaden that to say all electromagnetic radiation is 'heating' if it get absorbed. I had a
21W blue LED glue cure lamp (450nm), and I could definitely feel that on my hand.
LearnedAmateur - 21-10-2017 at 20:50
All electromagnetic radiation heats matter up, how efficiently is to do with how well the material absorbs particular wavelengths - laser pointers
above ~100mW can easily melt and/or set fire to dark objects in the visible wavelengths with a focusing mechanism. Microwaves heat food up because
they're absorbed very well by the OH bond in water, causing water molecules to vibrate by oscillating the bonds. Here's an absorption chart of peak
wavelength absorption of certain functional groups (these are normally used for IR spectrometry), this should give you some insight into why organic
compounds can be heated in this manner.
