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Author Topic: Colored Glasses?  (Read 3969 times)

Offline pileofrogs

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Colored Glasses?
« on: 03/08/2006 20:24:29 »
Ok, if I put on rose colored classes, I see the world in rose color becaues the glasses are only letting the rose color through.  Why is it that they look rose colored when I look at them as well as through them?  Shouldn't the rose color be going through and not back into my eyeballs?


 

Offline Solvay_1927

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Re: Colored Glasses?
« Reply #1 on: 03/08/2006 23:22:21 »
Hi (and welcome - I see it's your first post).

When you look AT the lens, most of the light that's coming from the lens to your eyes is light that's come from the OTHER side of the lense (e.g. it's light that's being reflected off the wearer's face, or off the table that the glasses are sitting on, or whatever).
So the non-rose-coloured wavelengths will have been absorbed by the lens and the light that reaches you is rose-coloured.

If you're not convinced, just think of this: If you covered the back of the lens with black paper, then the lens would look black, wouldn't it?
(Well, almost totally black, but not quite - it would look black with a bit of a rose-coloured hue.  This is because a small proportion of the light going into the front of the lens would get reflected by the lens - i.e. it doesn't ALL get through to be absorbed by the black paper.  But the light being reflected would not just be reflected by the surface of the lens - much of it is being reflected by the back of the lens, or even from half way through the lens - so much of the reflected light has still passed through the lens, and so it still looks rose-coloured.)

I'm not sure I've explained that too well, but hopefully it helps.
 

Offline Soul Surfer

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Re: Colored Glasses?
« Reply #2 on: 03/08/2006 23:27:28 »
No.  The reason for this is that most optical filters operate by absorbing the light that does not pass through them and you see the colour of the glasses by seeing objects illuminated by unfiltered light through them.  If you place the filter right on top of a white card and the light has to go through the filter and back the colour is even stronger.  there is however a class of filters known as "interference filters" that consist of partially reflecting surfaces at percise seperations to ensure that some colours pass through and others are reflected rather than absorbed.
(anti reflection coatings on lenses are a special case of this type of filter).  In this case the light reflected from the filter shows a complementary colour to the light that passes through.

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Offline pileofrogs

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Re: Colored Glasses?
« Reply #3 on: 04/08/2006 00:37:14 »
Awesome!  Thanks!
 

Offline daveshorts

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Re: Colored Glasses?
« Reply #4 on: 05/08/2006 01:24:31 »
Many things other than interference filters are different colours in transmission than reflection. Gold for one, if you look through a thin layer (a few nm) you see a beautiful blue colour, where as the reds and greens are reflected, hence the yellow colour of gold. An easier to achieve version of this is ohp pens on transparancies, if you look through them they are one colour, if you look at them from the side (so you see mostly the reflection from the surface) they often look like the inverse colour.
 

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Re: Colored Glasses?
« Reply #4 on: 05/08/2006 01:24:31 »

 

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