Glass Message Board
Glass Identification - Post here for all ID requests => Glass => Topic started by: Gary on January 24, 2015, 11:49:59 AM
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I was hoping someone could explain what causes this effect. The first image is taken with the the sun/daylight behind the bowl, which show a blue colour, and goes all round the top of the bowl. The second image is taken with the sun/daylight in front of the bowl, and there is no sign of any blue. These two images were taken with a macro lens.
The third image is a top view of this small bowl (9.5cm wide).
Gary
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This is one of the joys of what glass can do with colour, Gary. It's the difference between reflected and refracted light. There is no blue when the light is reflected from the surface of the glass, but when light is coming through the glass, which contains colours, those colours will stop certain wavelenghts of light coming through - so what you see is what is left over from the spectrum of the rainbow - blue light gets through, (all other colours are stopped) so that is what you see.
There can be an interesting effect in some bits of Mdina, which have a frothy yellow background with teal blue strapping on top. When light comes through these pieces, the colour you see from the addition of blue and yellow is purple.
When you mix paint, you get green from blue and yellow.
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hello Sue.......... can we use the word transmitted as an equal substitute for refracted......... or have I been getting it wrong all these years :)
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???
probably...
(I'm confuddled now.)
I mean light coming thoguh the glass, which yes, is transmitted. But the light gets refracted by the colours inside it, so it doesn't ALL get transmitted. Some wavelengths are held back.
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I've always thought of refraction as the business of how light can alter the position of how we see an object, when there's something like water or glass in the way - similar to when we view the pencil in a glass of water, and it appears not to line up. But you're right of course about light, when coming from behind something, produces colour variation and all the other clever techie bits etc. you mention.
Would you mind awfully though if I stick to using the word transmitted as the opposite of reflected - and you won't be cross :-* ;) ;)
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Not at all, Paul. I'm doubting myself anyway. ;D
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Nice description of both refracted and transmitted here on the Physics Classroom site
http://www.physicsclassroom.com/class/refrn/Lesson-1/The-Cause-of-Refraction
m
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http://en.wikipedia.org/wiki/Dichroic_filter (http://en.wikipedia.org/wiki/Dichroic_filter)