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BS: COLORED Shadow?

06 May 10 - 11:34 AM (#2901279)
Subject: BS: COLORED Shadow?
From: Ebbie

I realize that I ask really dumb questions and here's another.

Now, we all know that the reason that shadows are not in color is that, unlike reflections, the light is blocked, .

But last night I came upon a puzzler.

I went by a car parked in a lot. This car was white and on one side it had broad GREEN stripes. I thought at first that it must have been painted that way and then I saw that it was the same pattern as the fence railing alongside. The sidewalk (pavement) is upslope there as is the railing.)

There was a streetlight which hit the railing. I stuck my hand up into the light so that my hand's shadow was outlined on the car. My hand shadow was GREEN.

I walked around and checked the various shadows that that streetlight was casting- all of them were black, devoid of color, as was my own.

So. Was there something in the car's paint that created this phenomenon?


06 May 10 - 11:36 AM (#2901281)
Subject: RE: BS: COLORED Shadow?
From: Bert

It was the lighting. There was a green light shining which was not in shadow.


06 May 10 - 11:39 AM (#2901286)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

Nope, Bert. I checked. It was a street corner and there were no other lights.


06 May 10 - 11:50 AM (#2901298)
Subject: RE: BS: COLORED Shadow?
From: mousethief

Optical illusion, maybe? Like the classic optical illusion where you have red and green lines and it looks like there is yellow between them?


06 May 10 - 12:09 PM (#2901319)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

What sort of lights were there? Sodium, perhaps, which gives off a bluish color? Was there one of those orange lights nearby?


06 May 10 - 12:10 PM (#2901321)
Subject: RE: BS: COLORED Shadow?
From: Desert Dancer

Colored shadows are the result of different colored light sources in different positions. There might have been a light source you missed, or maybe there was something that was having a prismatic (light splitting) effect on the white light source that you saw. Possibly the fence was creating some light scattering that caused this effect.

http://www.learner.org/teacherslab/science/light/color/shadows/coloredshadowsbackground.html
http://www.exploratorium.edu/snacks/colored_shadows/index.html
http://blog.sciencegeekgirl.com/2009/05/27/physics-toys-tuesday-colored-shadows/

~ Becky in Tucson


06 May 10 - 12:11 PM (#2901322)
Subject: RE: BS: COLORED Shadow?
From: mousethief

The slits in the fence would have to be awfully skinny for that, wouldn't they? We're talking distances close to the wavelengths.


06 May 10 - 12:16 PM (#2901327)
Subject: RE: BS: COLORED Shadow?
From: Desert Dancer

In fact, it may be that the fence was acting as a http://www.answers.com/topic/diffraction-grating>diffraction grating (more precisely, a transmission grating).

~ B in T


06 May 10 - 12:23 PM (#2901336)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

In this link, http://www.exploratorium.edu/snacks/colored_shadows/index.html, the second illustration is the shade of green that I saw.

Rap: "Was there one of those orange lights nearby?"

Yes, the street lamp is more orange than white. However, everywhere else I looked, the shadows it cast were black. Why only on the white car was it green?

The fence, Desert Dancer, was/is one of those nondescript gray metal ones, rounded, probably hollow.

The fact that the color was the exact shade of green that Becky linked to makes me sure that this is what is going on, but I still don't know how. There is no other light in the area..

Is it possible that the street lamp itself is prismatic? But again: why were the other shadows black?


06 May 10 - 01:35 PM (#2901385)
Subject: RE: BS: COLORED Shadow?
From: Donuel

Even if there is only ONE light source you will see a colored shadow that is the opposite color of the source.

This phenomenon can be reproduced by looking at a colored light for half a minute and then close your eyes. The after image you see with your eyes closed will be the opposite color that you were looking at. Example a reddish light will make a green after image.
A yellow light will make purple. An orange light will make aqua.

Sodium lights are yellow to reddish, mercury can be bluish ect. so the dark areas of shadow will adopt an after image color.

The reason for the after image has to do with a chemical replenishment inside your eye cones that prepare them to send another signal to the brain.


06 May 10 - 01:50 PM (#2901399)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

I was thinking that blue from a "white" or "blue" sodium lamp coupled with the "yellow" component of the "orange" lamp could make green. There's a lot more questions that need answers, though. For instance, the angles of the lights, the condition of the bulbs (lamps), and so on.


06 May 10 - 02:15 PM (#2901417)
Subject: RE: BS: COLORED Shadow?
From: Bobert

Well, first of all, the shadow itself has no color but the object within the shadow do... Huh??? Yeah, that's right... There are some indirect light sources that do make it onto the objects that fall within the shadow... Those objects may look to be colorless because of the vast contrasts between the lighted area and those objects in the shadow... If you stand with yer back to the sun and look just at the shadowed area for a minute you'll plainly see that the objects within the shadowed area do indeed have colors...

Now we know that in order for us to percieve color we do need a source of light... Indirect light can be very tricky but also fascinating because it picks up the colors from the objects it either reflects off of or through... The phenomina of "gold light" that artist love and which we occasionally see just before the sun is about to go down comes from direct light from the sun passing thru atmosphere and pickin' up the colors of dust and water that is in that atmosphere...

So, Eb... Yer not going nuts... Okay, maybe you are but not because you percieved green in those shadows becuase it most likely was green...

BTW, here's a fun one when it come to color... If you take and make a pinwheel with 7 equal slices (like pie) and each is painted the one of the 7 primarary colors and you spin the pinwheel fast enough it appears to be...

...white... Yup, white is really an equal mix of all the primary colors...

(See, mom... Now aren't ya' gald to halped me thru art school??? I mean, other than the collection of paintings, prints and pen & inks that you got out of the deal??? lol...)

B~


06 May 10 - 02:36 PM (#2901430)
Subject: RE: BS: COLORED Shadow?
From: Amergin

I think you need to stop eating mushrooms.....


06 May 10 - 02:45 PM (#2901433)
Subject: RE: BS: COLORED Shadow?
From: GUEST,999

Amergin, great minds . . . .


06 May 10 - 02:56 PM (#2901441)
Subject: RE: BS: COLORED Shadow?
From: GUEST,Wolfgang (no cookie)

Nothing to do with intoxication of any kind, just Ebbie's close and good observation of a natural phenomenon that is due to characteristics of our visual system.
I'm rather sure that Goethe has already described something similar.

Why on the white car only?

The effect was also everywhere else but was "drowned out" by other colours. On the colourless white background, however, it became visible.

Contrast effect (simultaneous and successive) are also best seen on a plain white background.

Wolfgang


06 May 10 - 03:05 PM (#2901445)
Subject: RE: BS: COLORED Shadow?
From: GUEST,999

Speaking of great minds . . . .

Thanks, Wolfgang.


06 May 10 - 03:11 PM (#2901451)
Subject: RE: BS: COLORED Shadow?
From: MMario

I suspect it was an artifact of the paint/finish on the car.


06 May 10 - 03:25 PM (#2901459)
Subject: RE: BS: COLORED Shadow?
From: katlaughing

Not so fast in dissing Bobert, there, guys. I have one of his exquisite pen and ink drawings and he knows what he is speaking of, artistically, which is all about light, colours, etc.


06 May 10 - 04:01 PM (#2901491)
Subject: RE: BS: COLORED Shadow?
From: GUEST,KP

I suspect that the white paint on the car was fluorescing slightly. It would be too faint to show up under direct light but removing other light sources or shading them might cause it to be visible. A quick google reveals this as an example;
http://www.nwepaints.co.uk/acatalog/LuminousFluorescent.html

KP


06 May 10 - 04:11 PM (#2901502)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

There's too many variables here to make a definitive answer, so let's apply Occam's Razor and assume the simplest hypothesis as the correct answer: Ebbie is radioactive (probably kryptonite) and was creating her own Green Shadow (which will soon be in a comic book near you).


06 May 10 - 04:13 PM (#2901506)
Subject: RE: BS: COLORED Shadow?
From: McGrath of Harlow

Ignore these muggles...


06 May 10 - 05:40 PM (#2901556)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

What boggled me teeny mind was the boldness of the color. There was nothing diffused about it; it was as solid a green as the pencil in front of me (Actually I don't have a pencil in front of me but you get the idea).

Incidentally, when I said that the *outline* of my hand was the same green I actually meant the *silhouette*.

I'm going out there again tonight. If there is a red car there, say, what will be the color?

"Mushrooms"? humph


06 May 10 - 07:04 PM (#2901626)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

Bobert and Donuel have nailed it. All the rest is just conspiracy theory, based in insufficient education in the subject area. :-)


06 May 10 - 07:27 PM (#2901644)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

I still think it's kryptonite.


06 May 10 - 08:05 PM (#2901665)
Subject: RE: BS: COLORED Shadow?
From: Bobert

Might have been kryponite, Rap...

BTW, thanks, kat... I'd like to think that I learneda little something my second go-round thru college... I mean, the 1st go-round was to make my parents happy but going back and getting a degree in Fine Art was to make me happy...

BTW, on the subject of light... The Van Eycks (Jan and Hubert(, painted the "Aletrpiece in Ghent" in like the early 1400s and in the top center panel they painted jewels... No make that, they created jewels with paint (meduim and pigment) to such a degree that the jewels have a 3D quality and if you look at a jewel from one side verses the other there is a distinct difference in what you see in the way of color based solely on the differences of light sources from one side to the other...

This is kinda what we are talking about here...

B~


06 May 10 - 09:35 PM (#2901696)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

I must say, Bobert, that my first thought was that they were 'racing' stripes. Tonight, when I walk the dog, I'm going to take along some white paper, just in case there is no white car. Any best on whether the paper will stripe green?


06 May 10 - 10:13 PM (#2901712)
Subject: RE: BS: COLORED Shadow?
From: Bobert

Light is way to funny fir that, Eb, but if conditions are the same and it the car was actually white, which it may not have been but light green, then I'd say that you'll get the green stripes again...

BTW, when I first learned about white being all the colors and black being the absence of color I found it real interesting that "colored people" where the white folks... But nevermind that... On with yer experiement and let us know...

Also, check out where yer light sources come from... There are usaully more than the obvious...

B~


06 May 10 - 10:31 PM (#2901727)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

Actually, Bobert, white is the absence of "darkons" -- particles of darkness. The so-called "photons", or light particles, are actually absence of darkons. See, what we call lights actually are darkon-suckers and when you turn them suckers off darkons are left to themselves and not sucked up.

I can show you the math for this if you have time for it.


06 May 10 - 10:31 PM (#2901728)
Subject: RE: BS: COLORED Shadow?
From: mousethief

If you find a person whose skin is lacking all color, run.


06 May 10 - 10:45 PM (#2901739)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

Ah Rapaire,

I think you may have the maths behind Pratchet's theory on "The Speed of Darkness".


06 May 10 - 11:19 PM (#2901765)
Subject: RE: BS: COLORED Shadow?
From: Rapparee

Makes as much sense one way as the other.


07 May 10 - 01:49 AM (#2901808)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

Well, I don't know much more about the why-fors but I have a little more information.

I just got back from my walk-

The street lamp colored the white paper turquoise, as was mentioned above somewhere. It also colored a section of newspaper I took along for the purpose; it was not as bright as on the white paper but definitely turquoise.

A bit later at a greater distance from the lamp I checked a white U-Haul truck- and the sideview mirror cast a turquoise shadow on the door.

Turquoise, not green.

I think it was a little later last night than tonight (about 10 o'clock versus 9:30) making it just that bit darker out; I don't know how much difference that would make?


07 May 10 - 04:06 AM (#2901838)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

Depends on what your eyes were looking at before - and what colour mix they got 'used' to just before, as per Donuel's comment above.


07 May 10 - 07:36 AM (#2901936)
Subject: RE: BS: COLORED Shadow?
From: Bobert

Well, we're certainly zeroin' in on this one...

Next??? Who kidnapped the Limburg's baby???

B;~)


07 May 10 - 08:11 AM (#2901966)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

"Who kidnapped the Limburg's baby???"

ichmael?


07 May 10 - 12:01 PM (#2902109)
Subject: RE: BS: COLORED Shadow?
From: GUEST,999

"Who kidnapped the Limburg's baby???"

A cheese company.


07 May 10 - 12:05 PM (#2902114)
Subject: RE: BS: COLORED Shadow?
From: GUEST,999

Ebbie, it`s OK. We love you anyway.


07 May 10 - 12:24 PM (#2902129)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

ha :)


07 May 10 - 08:50 PM (#2902453)
Subject: RE: BS: COLORED Shadow?
From: GUEST,999

Here`s yer answer, Ebbie.


07 May 10 - 09:29 PM (#2902466)
Subject: RE: BS: COLORED Shadow?
From: GUEST,Guest from Sanity

Hi Ebbs...some car paint jobs are done in 'pearl'. Depending on the type of pearl, the reflections and light reflections can vary from color to color. For instance, the is a 'blue pearl', some rainbow(you'd like that one), some silver-green, some pink, and so on and so forth. Ok?

GfS


07 May 10 - 09:31 PM (#2902468)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

Yep - as we said before...

OK, don't believe me, honestly, I just don't know why I bother - people just ignore me - here I am with all this knowledge, IQ the size of a planet, and nobody takes any notice, and I've got this pain all down the diodes in my left side...


07 May 10 - 09:33 PM (#2902469)
Subject: RE: BS: COLORED Shadow?
From: GUEST,Guest from Sanity

'Shrooms'????

Wink!
GfS


07 May 10 - 09:49 PM (#2902474)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

nope - 42...


08 May 10 - 05:23 AM (#2902567)
Subject: RE: BS: COLORED Shadow?
From: s&r

Sodium vapour lamps have a well defined and discontinuous spectrum. This gives strange effects. Commonly for example red lipstick under a (yellow) sodium lam looks black. This is because there is no common hue that the red lipstick can reflect.

A yellow lamp from a (say) tungsten source has a range of frequencies present from red through blue with a peak in the yellow area. Rhe red component of the light is reflected by the lipstic and show red.

Fluorescent lamps hav a dscontinuous spectrum, and often a 'daylight ' fluorescent lamp will produce a green cast on a photograph.

Stu


08 May 10 - 05:36 AM (#2902568)
Subject: RE: BS: COLORED Shadow?
From: s&r

The spectra of various sources are shown on http://www.google.co.uk/imgres?imgurl=http://bmb.lcd.lu/science/compared_spectra.jpg&imgrefurl=http://bmb.lcd.lu/science/index.html&usg=__MGZyK8rBgvGZkgfu9Fz1ViJW09M=&h=357&w=388&sz=12&hl=en&start=17&um=1&itbs=1&tbnid=MkaZz_BjLo50ZM:&tbnh=113&tbnw=123&prev=/images%3Fq%3Dmercury%2Bvapor%2Blamp%2Bspectrum%26um%3D1%26hl%3Den%26client%3Dfirefox-a%26sa%3DX%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1.

The link maker didntt like the address I think.

Stu


08 May 10 - 10:45 AM (#2902690)
Subject: RE: BS: COLORED Shadow?
From: Desert Dancer

astro, my husband the physicist, says my diffraction grating theory is full of holes and refuses to speculate on the situation.

Oh, well!

~ Becky in Tucson


08 May 10 - 12:11 PM (#2902724)
Subject: RE: BS: COLORED Shadow?
From: Ed T

Color depends on the light source (at night, sodium vapor streetlights, fluorescent, incandescent), and the reflection characteristics of the surface. Perceived color also depends on how the eye and brain process the light coming into the eye, and apparent color changes with influences of the color of surrounding objects.

Also, the perception of color (which may vary from person to person) changes in low-light conditions. In good light conditions, the human eye distinguishes color with three receptor types (cones) with peak sensitivities in the red, green and blue. They are not sensitive enough to provide much useful vision at night (low light). There is a separate set of receptors (rods) with much higher light sensitivity that come into play at low light (night) but they do not give good color information. There is only one set of these in the human eye with a peak response in green.

Also the eye and brain try to adjust the color corrects for the color of the light shining on it and what it deduces the color should be. That is why grass still looks green even when you see it under the red light of sunset.


08 May 10 - 12:13 PM (#2902726)
Subject: RE: BS: COLORED Shadow?
From: Ed T

I have also noticed that when I take night pictures near sodium vapor streetlights quite often there has been a noticible green influence.


08 May 10 - 04:08 PM (#2902750)
Subject: RE: BS: COLORED Shadow?
From: Ebbie

OK, I'll try again. I'm beginning to wish I had never noticed it! Not true, actually; I don't mind feeling dumb if I end up learning something.

Robin, it was not the effect of an after-image. Everyone older than 6 is familiar with that effect. This was a sustained, bright, crisp, sharp, Irish green image as clear as racing stripes on .

On the white paper it was a much more muted color- and the color was turquoise, tending to blueish.

On the newspaper it was even more diffused but still turquoise.

There is no other light source there. This is Juneau, Alaska; our streets are narrow and we don't have lamp posts on every corner.

It was not full dark either time (half hour difference, two different nights). The days of the month of May are rapidly lengthening. Soon the sun won't set until after 10:00 and the sky will be the shade of stone-washed blue jeans. As yet it is darker than that but even now it is twilightish.

So only one lamp. Most likely sodium; the emitted light is orangeish in shade. My question at this point: Are sodium lamps' lights made up of different colored 'cones' so that they break apart in prismlike fashion?


08 May 10 - 07:37 PM (#2902845)
Subject: RE: BS: COLORED Shadow?
From: The Fooles Troupe

As someone else said, "diffraction grating theory is full of holes"... . hehehehe -

Ebbie -

The fool who thinks he is a fool is for that very reason a wise man;
But the fool who thinks he is a wise man is rightly called a fool.


Here is your Zen of the Day:
The ten thousand questions are one question. If you cut through the one question, then the ten thousand questions disappear.


:-)

I have speculated all I can with the available information, sorry... I call defeat de feet ... :-)


08 May 10 - 08:16 PM (#2902860)
Subject: RE: BS: COLORED Shadow?
From: Ed T

"Red MnMs, green MnMs, they all wind up the same color in the end."