Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: glitch on 27/09/2004 14:59:32
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Hello i am new to the forum and have an interesting question. I have been unable to find out any information on how or what colors effect UV rays. i am doing an experiment on how color light effects the growth of a plant but i need to keep the UV rays out. i will make a box of one color paper or sheet and test each color and how the plant grows. if you know where i can find any info on this please contact me at civilwarpatriot@yahoo.com and say from science forum or else i wont open the email caus ei dont know who u are. thanx and God bless.
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The "color" of an object or a filter has to do with the chemical makeup of the material and how it interacts with photons of different wavelengths. You cannot generalize that material of a certain color will always affect UV rays in a certain way because visible light and UV are different wavelengths. Some materials (such as glass) block most UV while passing most visible and others will pass UV while blocking most visible.
Welcome to the forum and good luck with your experiment. I'm sure others will have a better answer for you.
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John - The Eternal Pessimist.
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There is also the distinction between UVA and UVB as well. UV has a broad range of wavelengths and some UV blocking materials only block a portion of the UV spectrum.
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This may sound silly, but the colour that will block UV is the colour that will block UV light... eg purple is the colour that will block green light, and yellow is the colour that will block blue light... this doesn't help you much.
Depending on the dye things that block blue light will probably be even better at blocking UV light, so use yellow or red filters...
The other option would be to get some transparent suncream which is designed to just block UV and sandwich it between two layers of something transparent to stop it drying out. Or I think normal glass will block UVB quite well.
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Flowers which appear to be one color in visible light can have patterns visible only in UV light. This is because insects (not sure if it's some or all) can see into the UV range of light. The same visible color of paint made through different process can be completely different in the UV range. There's no way to tell without a camera that records UV ranges and experimentation.
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The colour that would block UV would just look white to us since we can't see UV light. The sunsceen idea is good because it's specifically designed to stop UV light. You can also go to a junkyard and 'borrow' a tinted window or get a piece of glass tinted at one of those car shops.
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You might find this interesting.
http://www.newton.dep.anl.gov/askasci/phy00/phy00890.htm
Also, I know that silica (normal) glass absorbs significant amounts of UV, so lenses for working with UV are usually made from quartz.
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Given that any coloured filter also absorbs visible light you obviously have a problem. However polycarbonate is an effective UV-filter, absorbing 90 % of light below 410 nm and 99.99 % below 400 nm, glass absorbs mostly below 320 nm which is clearly less effective as 400 nm is the generally excepted UV/visible boundary. 5 mm or thicker is ideal and is about the thickness of the samples i just tested.
Polycarbonate should be available to you, as it is shatter resistant it is used as safety glasses, blast shields etc and is available around most labs, school or otherwise.
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quote:
Originally posted by Quantum cat
The colour that would block UV would just look white to us since we can't see UV light. The sunsceen idea is good because it's specifically designed to stop UV light. You can also go to a junkyard and 'borrow' a tinted window or get a piece of glass tinted at one of those car shops.
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Hi all, just found this place thru some random googling. I need to find a shop in the UK which can do me about 4m sq of UV filter glass to protect my books, if anyone knows of anywhere which will do this please please let me know. I think there might be some sort of UV filtering acetates or varnish I might also use...whenever I try googling such things I keep getting lots of physics type info that I really can't translate into english! Does anyone know what range of UV light affects books in terms of fading etc, apparently UV comes in between 0-400 nm but i'm not sure if I need to block all of this and presumably only blocking the relevant rays might be cheaper...please mail me if you can help at all - thanks :-D
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The polycarbonate I suggested would be a good start. However, all light will fade colours eventually, including the visible. Either make doors infront of your bookshelves or leave them out of the direct sunlight. Polycarbonate is your best bet if you wish to display them. I'm not sure where you might buy it, B&Q, a builder's merchant or a garden centre might be a good start. Be sure that you are being sold polycarbonate though and not some other plastic, as in my experience non-chemists use terms like polycarbonate, perspex or whatever imprecisely.
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It's available as a foil, in glass it gets pressed between two sheets:
http://www.campingworld.com/browse/products/index.cfm?deptID=&subOf=2&prodID=3287&src=TSC
The living are the dead on holiday. -- Maurice de Maeterlinck (1862-1949)
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I'm not sure about this problem, some eyewear manufacturers developed orange/yellow/brown lens and claim they all can filter UV and blue light.
You need to detect that using sophisticated apparatus. As an programmer who stares at multiple computer screens 8-10 hours a day, I bought a pair of computer glasses from Taime Optics(http://www.halovis.com) a few weeks ago, they claim that the eyewear can filter 97% of blue light and 100%, I'm still not sure I really need this, but feel much better when staring in front of the computer.
The images belows are the test results(with or without the bluelight protection glasses)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.halovis.com%2Fimages%2F23.jpg&hash=88ca17fefb3f938d3a1e26ef67f8daf7)
(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.halovis.com%2Fimages%2F12.jpg&hash=ff921fc0ead0ae27b01100dee1148621)
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http://www.ncbi.nlm.nih.gov/pubmed/19614895 (http://www.ncbi.nlm.nih.gov/pubmed/19614895) suggests that common glasses absorb ultraviolet to varying degrees.
Also worth checking on polycarbonate. Clear Perspex is fairly transparent to UV but polycarbonate appears to absorb it almost entirely. Pity! I'm used to getting a good suntan in my old aeroplane but the new one has a polycarbonate canopy!
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I'm not sure about this problem, some eyewear manufacturers developed orange/yellow/brown lens and claim they all can filter UV and blue light.
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UV is < 400nm : from your meter the screen isn't emitting UV ... http://en.wikipedia.org/wiki/Ultraviolet#Subtypes
You could achieve the same effect as the yellow glasses by turning down the blue in the monitor(s).
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I'm not sure about this problem, some eyewear manufacturers developed orange/yellow/brown lens and claim they all can filter UV and blue light.
You need to detect that using sophisticated apparatus. As an programmer who stares at multiple computer screens 8-10 hours a day, I bought a pair of computer glasses from Taime Optics a few weeks ago, they claim that the eyewear can filter 97% of blue light and 100%, I'm still not sure I really need this, but feel much better when staring in front of the computer.
The images belows are the test results(with or without the bluelight protection glasses)
To me, this reads like an advert, especially since the actual reported data don't show a problem for the product to solve