The Naked Scientists

The Naked Scientists Forum

Author Topic: Do white coloured objects reflect infrared radiation?  (Read 20571 times)

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #25 on: 29/01/2009 05:18:32 »
Damn it! It isn't working, the beaver got in!!!
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #26 on: 29/01/2009 05:19:45 »
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?

--------

http://en.wikipedia.org/wiki/Ent

« Last Edit: 29/01/2009 05:27:04 by yor_on »
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #27 on: 29/01/2009 05:24:26 »
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"
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #28 on: 29/01/2009 05:25:14 »
Oh please Mr. yor_on, you've been reading way too much Tolkien!
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #29 on: 29/01/2009 05:38:50 »
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'

 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #30 on: 29/01/2009 05:40:17 »
Are you going to sleep?
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #31 on: 29/01/2009 05:45:19 »
Okay, enough said, you must have fallen asleep.
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #32 on: 29/01/2009 06:43:48 »
What are you still doing here? Go to sleep!
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8645
  • Thanked: 42 times
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #33 on: 29/01/2009 06:53:38 »
Morning all.
The answer to the question is  "generally yes".
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #34 on: 29/01/2009 06:55:58 »
Why didn't you just say so earlier?   :D:D I was stuck with Mr. yor_on for two hours!! ;D ;D ;D
 

Offline Glyph

  • First timers
  • *
  • Posts: 8
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #35 on: 29/01/2009 07:27:30 »
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 ...




                       regular monochrome                                                      Infrared monochrome

newbielink:http://en.wikipedia.org/wiki/File:Rudin-house.jpg [nonactive]

newbielink:http://en.wikipedia.org/wiki/Infrared_photography [nonactive]
« Last Edit: 29/01/2009 07:39:28 by Glyph »
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #36 on: 29/01/2009 07:43:04 »
Hey, that is really neat Glyph, thank you! :)
 

Offline Bored chemist

  • Neilep Level Member
  • ******
  • Posts: 8645
  • Thanked: 42 times
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #37 on: 29/01/2009 20:29:49 »
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.
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #38 on: 29/01/2009 20:59:31 »
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".
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #39 on: 30/01/2009 11:23:22 »
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?
« Last Edit: 30/01/2009 11:28:35 by yor_on »
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #40 on: 30/01/2009 11:24:49 »
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #41 on: 30/01/2009 11:29:27 »
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!
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #42 on: 30/01/2009 18:56:19 »
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:)
???
Quote
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
 

Offline Glyph

  • First timers
  • *
  • Posts: 8
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #43 on: 30/01/2009 19:33:00 »
Here is a better example of what I meant ...



newbielink:http://www.usatoday.com/news/world/2008-08-27-3508714940_x.htm [nonactive]

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.
« Last Edit: 30/01/2009 19:36:07 by Glyph »
 

Offline Soul Surfer

  • Neilep Level Member
  • ******
  • Posts: 3345
  • keep banging the rocks together
    • View Profile
    • ian kimber's web workspace
Do white coloured objects reflect infrared radiation?
« Reply #44 on: 31/01/2009 00:16:54 »
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!
 

Offline yor_on

  • Naked Science Forum GOD!
  • *******
  • Posts: 11978
  • Thanked: 4 times
  • (Ah, yes:) *a table is always good to hide under*
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #45 on: 31/01/2009 05:30:23 »
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?
« Last Edit: 31/01/2009 05:32:43 by yor_on »
 

Offline Chemistry4me

  • Neilep Level Member
  • ******
  • Posts: 7709
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #46 on: 31/01/2009 05:33:13 »
Hmmm... so you do know your waves.
 

Offline swansont

  • Full Member
  • ***
  • Posts: 62
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #47 on: 04/02/2009 11:10:28 »

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
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Do white coloured objects reflect infrared radiation?
« Reply #48 on: 04/02/2009 13:01:58 »
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.
 

The Naked Scientists Forum

Do white coloured objects reflect infrared radiation?
« Reply #48 on: 04/02/2009 13:01:58 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums