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As answered in this question, transparent bricks are made of PC (polycarbonate) and as listed in this answer and on Brickipedia there are fourteen transparent colors:

40  Transparent (clear) 
41  Transparent Red 
42  Transparent Light Blue  
43  Transparent Blue    
44  Transparent Yellow  
47  Transparent Fluorescent Reddish-Orange (Transparent Dark Orange)    
48  Transparent Green   
49  Transparent Fluorescent Green (Transparent Neon Green)  
111 Transparent Brown (Smoke)   
113 Transparent Medium Reddish-Violet   
126 Transparent Bright Bluish-Violet    
143 Transparent Fluorescent Blue    
182 Transparent Bright Orange   
311 Transparent Bright Green

I am interested in the exact optical properties Transparency and translucency of this colors. How much percentage of light is absorbed? Has anyone measured with a prism which wavelength gets filtered out for each color?

P.S.: Why do I want to know? I want to put different kinds of LEDs in transparent bricks and like to know how the light is influenced. There are LEDs in different colours (light temperature) and one can calculate the luminosity at specific voltage and current. I'd like to calculate the luminosity as modified by the polycarbonate which the LEDs are put into.

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If the question is 'How would you measure this?', you would probably be able to get some help from Physics.SE. I would assume you would need a fairly sensitive light sensor to detect the differences in reflected light. – Ambo100 Oct 16 '12 at 15:56
Do you want an homemade method for doing this at home? – pcantin Nov 29 '12 at 3:18
@jakob Any more info you could give us? If you answer the questions from Ambo100 and I we could move forward with this question. – pcantin Dec 7 '12 at 17:22
I don't want to measure this but I'd like to have some numbers, charts, technical specifications etc. to know how light from specific LEDs would be changed. – Jakob Dec 7 '12 at 20:05
There are more transparent colours than what's posted in this question. The optical characteristics vary a lot between parts. It depends on the age of the part, its condition, and what kind of part it is. Also the parts are not manufactured to precise optical characteristics, so any two batches of parts of the "same" colour might have different properties. I'm not sure you can get a crib sheet for this, you'd be better off just experimenting with the bricks you get. – Mr. Shiny and New 安宇 Jul 5 '14 at 2:01

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