Naked Science Forum
General Science => General Science => Topic started by: Chemistry4me on 29/01/2009 03:23:17
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[???] [???] [???] [???] [???]
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fundersun%2F3.gif&hash=5556ef1a6f4d01e97e3b2d36ecfd0dd7)
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When using illumination it should be visible.
It's just like any other light.
I think??
You know, photons bouncing, having a good time..
Or am I missing something here?
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I don't know, you're the physicist, you tell me, please [:)](https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fbeging%2F5.gif&hash=c2e58aeb72fec5f517f6860c7cba6635)
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Night intensifiers work differently though.
"They focuses the light (photons) on a 'photocathode'.
The cathode release electrons which are then are 'energized' by bouncing around in a electric field as well as generating even more electrons by specially coated walls.. This makes for a denser electron cloud representing an intensified version of the original image.
And they are passive.
Just like cooled infrared detectors.
Cooling the detectors to around -160 C gives them a very extreme sensitivity and without that cooling the detectors would be flooded by their own radiation.
It's only like ten percent of the light from the Sun that comes down as infra red radiation.
So there is not much around:)
But if you're thinking of 'thermal night vision' which also are in the infra red spectrum you are making excellent sense, as well as making me curious:)
That as all living tissue emit infrared energy (temperature).
Those can see through both smoke and fog.
And those are also 'passive'
If you use such then white materials absorb the least 'heat' and therefore will be hardest to 'see'.
Or if you use material created to contain infra red (heat).
What do you need it for?
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Ah, Mr Chem.
Nope, I'm not.
But it was a nice idea.
Thanks
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I don't need it for anything, I was just being curious. [:)]
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But if you're thinking of 'thermal night vision' which also are in the infra red spectrum you are making excellent sense, as well as making me curious:)
What is this? You know a lot more about it than me, I'm curious as to what you are thinking too!
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What? You're not a physicist? [???][???][???]
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Looking at what I wrote, I think there is a 'curse' on me.
It's called 'modify' at this site:)
That's why I need to learn how to spell.
Each one his own warlock:)
And no, you know an awful lot of chemistry right:)
Do you work with it?
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No, I do not work with chemistry, and I don't know an awful lot about it either!!
You're just a fan of physics right Mr. yor_on?
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Well we're both 'fans' I think.
You're a fan of primary Chemistry if I understand you right?
I'm more 'physical'.
No big difference there.
Together we will conquer:)
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Primary chemistry? What do you mean by that?
Together we will conquer:)
Yes, indeed. (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Farmy%2F4.gif&hash=a7f297417304264894c21d78d39f9153)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Farmy%2F4.gif&hash=a7f297417304264894c21d78d39f9153)
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Well your name gave me a clue I have to admit.
As well as this:)
http://www.thenakedscientists.com/forum/index.php?topic=11612.msg221718#msg221718
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Okay, it is the only thing that I know!! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fcheering%2F1.gif&hash=6728e488f6a57a0c07d0e73171a595ab)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fclapping%2F5.gif&hash=84082ae1375d85f65239829d6b135af8)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fclapping%2F5.gif&hash=84082ae1375d85f65239829d6b135af8)
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Shouldn't you get some rest Mr. yor_on? (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fsleeping%2F1.gif&hash=0ccb6d36546e119637ee7668d0e83294)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fsleeping%2F1.gif&hash=0ccb6d36546e119637ee7668d0e83294)
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Aha, was it a quiz.
Nah, it's cool, thermally speaking:)
I'll sleep tomorrow:)
Tell me, do you have an inkling for the sweet and 'leisury' life of the armed forces?
It's just an impression I got from a former conversation.
I can't help but wonder.
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Btw: that flag?
Shouldn't it be Swedish?
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Sweet and 'leisury' life aye?? No, I am not planning to join the SAS any time soon!! [:)]
Yeah, sorry, I couldn't find a Swedish flag. [:I][:I]
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Doesn't matter:)
Otherwise i've heard that some of the best soldiers come from 'under there'
(Kiwis and Maoris:)
Australia have their own SAS units, right.
Is it the same in New Zealand?
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I don't really know much about the army, New Zealand has a small army, because no-body is going to attack us (at least that is what the government thinks), hee hee, mwahaaa (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fevil%2F3.gif&hash=0ece0c60d4fafad186e71ebdd538e4ca)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fevil%2F3.gif&hash=0ece0c60d4fafad186e71ebdd538e4ca) hahaaha
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Well, I've heard about some real dangerous Beavers on the loose.
Warn them...
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Don't worry, I'll take care of this! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Farmy%2F10.gif&hash=dbec6480d0596cc7d198063cf12faa24)
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Look away Mr. yor_on! This is getting violent! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fviolent%2F15.gif&hash=1b7788a773bef935ed5fbf575798b292)
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Mr chem, are you sure you're not 'connected'?
This is starting to look dangerous.
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WAIT A MINUTE! There are no beavers in New Zealand!!!
I think you might have meant possums Mr.yor_on.
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Nope, gotta warn you, there are beavers loose everywhere!!!
And they are masters of deception.
One even succeeded to get into my laptop.
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Oh no! I must boost the security on my computer!
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Damn it! It isn't working, the beaver got in!!! (https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Fcomputer1%2F10.gif&hash=59b211b6834ac63caa9ed078f4370463)
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Don't worry, he turned out to be a friendly chap.
It's not like a virus or anything.
They are mostly brown and can weight up to several pounds I've heard.
But you better take down all trees and carry them into your chamber.
Otherwise they soon will be gone.
But you're used to that in New Zealand, right?
Didn't you have 'Ents' under there recently?
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http://en.wikipedia.org/wiki/Ent
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You know.
"New Zealand, Home of the Middle-earthers."
Well sort of?
http://www.newzealand.com/travel/about-nz/culture/lotr/lotr-02.cfm
We too have a slogan.
"Sweden the home of the middling nutters"
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Oh please Mr. yor_on, you've been reading way too much Tolkien!(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Freading%2F4.gif&hash=c2ddb536a44e8a77377958948f3e4c2e)(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fbestsmileys.com%2Freading%2F4.gif&hash=c2ddb536a44e8a77377958948f3e4c2e)
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No way, to little I would say.
Mr Chem, its been a pleasure exchanging information with you.
And as we, each one, seems to have a beaver:)
Well, not really.
You know...
Figuratively speaking?
Mine is screaming btw.
To 'shut the *** up' and stop laughing.
We better finish this chapter as fast as humanly possible.
There are nothing so worrisome as to be worried by the presence of an avenging angel.
As this one is angling for my life, it seems.
So Mr Chem I will leave you with this old Chinese saying.
Apropos beavers.
'One bird in the hand is worth two in the bush'
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Are you going to sleep?
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Okay, enough said, you must have fallen asleep.
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What are you still doing here? Go to sleep!
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Morning all.
The answer to the question is "generally yes".
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Why didn't you just say so earlier? [:D][:D] I was stuck with Mr. yor_on for two hours!! [;D] [;D] [;D]
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The reflectance of a surface is not necessarily the same for all wavelengths of electromagnetic radiation, e.g. vegetation strongly reflects IR so appears much whiter in an IR monochrome image than in a regular monochrome (black & white) photo ...
[ Invalid Attachment ]
regular monochrome Infrared monochrome
http://en.wikipedia.org/wiki/File:Rudin-house.jpg
http://en.wikipedia.org/wiki/Infrared_photography
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Hey, that is really neat Glyph, thank you! [:)]
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Why didn't you just say so earlier? [:D][:D] I was stuck with Mr. yor_on for two hours!! [;D] [;D] [;D]
Because it was some stupidly early hour of the morning.
BTW, Glyph, thanks for the image but I think that saying "The reflectance of a surface is not necessarily the same for all wavelengths of electromagnetic radiation" is only informative to someone with no colour vision.
Incidentally, at some wavelength the white stuff will absorb IR but, for near IR, white things are likely to reflect IR just as they reflect visible light. There's nothing magical about the cutoff between one form of radiation and the other- it just happens to be the way our eyes work.
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BTW, Glyph, thanks for the image but I think that saying "The reflectance of a surface is not necessarily the same for all wavelengths of electromagnetic radiation" is only informative to someone with no colour vision.
He was not very precise, he should have written "The reflectance of a given surface is not necessarily the same for all wavelengths of electromagnetic radiation, even if, for that surface, it's the same for all the wavelenghts in the visible range".
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Didn't think of that:)
But it's true that IR and 'near IR' is just near, not the same.
But what color would then be the most reflective?
off white:)
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I've also learnt that dark blue is one, or the one, of the most 'difficult' colours for us to see when dusk is 'falling in'.
Any views on that?
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(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.freesmileys.org%2Fsmileys%2Fsmiley-confused013.gif&hash=396386a856152a890252526964cc44dd) (http://www.freesmileys.org)
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I've also learnt that dark blue is one, or the one, of the most 'difficult' colours for us to see when dusk is 'falling in'.
Any views on that?
Nope!
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Didn't think of that:)
But it's true that IR and 'near IR' is just near, not the same.
But what color would then be the most reflective?
off white:)
[???]I've also learnt that dark blue is one, or the one, of the most 'difficult' colours for us to see when dusk is 'falling in'.
Any views on that?
The sensitivity of retina for colours at the tails of the sensitivity curve is lower; the peak is on the green-yellow, so others colours are perceived worse, so when the light is dimmer, you can't perceive reds, oranges and blues anylonger, while you still perceive green-yellow. However the effect is complicated because when cones stop functioning, the rods are left functioning and they have another visibility curve; their peak is on the blue-green; see also "Purkinje effect":
http://en.wikipedia.org/wiki/Purkinje_effect
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Here is a better example of what I meant ...
[ Invalid Attachment ]
http://www.usatoday.com/news/world/2008-08-27-3508714940_x.htm
Un-inked areas of the scrolls which appear almost black in visible light are much brighter in IR.
The reflectance of visible light and the reflectance of IR from a surface do not necessarily correlate.
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I had an unexpected direct experience of this many years ago when I was working on an idea for improving infra red fire detectors which could be subject to gradual degradation due to their windows getting dirty or the visibliity of the flickering heat of a fire being obscured by smoke. I was using a broad band flash tube to generate a bright infra red flash to test them in a large fire testing chamber which was very black sooty dirty and dark because of all the things that had been built in it and set alight to test various aspects of fire safery detectors and extinguishants. The results were not what we expected until we realised that at the infra red frequences we were using the whole room looked like it was painted brilliant white!
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http://www.echeng.com/photo/infrared/tutorial/
It was this I meant with near Ir as compared to IR Lightarrow:)
What you wrote about dark blue was interesting.
I've always wondered if that was correct, but those teaching it was quite serious.
So it might work at dusk then, but not when getting real dark?
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Hmmm... so you do know your waves.
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I've also learnt that dark blue is one, or the one, of the most 'difficult' colours for us to see when dusk is 'falling in'.
Any views on that?
Blue, in general, is difficult to see because your eye isn't as efficient at the extreme wavelengths. But when your eyes become dark-adjusted, it's easier to see blue (scotopic vs photopic vision)
http://hyperphysics.phy-astr.gsu.edu/Hbase/vision/bright.html
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Blue, in general, is difficult to see because your eye isn't as efficient at the extreme wavelengths. But when your eyes become dark-adjusted, it's easier to see blue (scotopic vs photopic vision)
http://hyperphysics.phy-astr.gsu.edu/Hbase/vision/bright.html
Yes, that is exactly the reason of the Purkinje effect I was talking about in my previous post.