JohnWW
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Measuring the UV absorbance performance of sunglasses
This is a recent post of mine on the Thechemistrycluster Yahoo group, replying to a query, slightly amended:
Q: How can I test the UV protection of my sunglasses?
A:
You would need some sort of adapted or improvised wavelength-scanning photometric spectrometer for use on sunlight transmitted by the sunglasses,
which does not involve the transmitted light diffracted by being passed through a prism of a transparent material which absorbs UV light, or with
other optics made of such a material. This rules out a refracting prism made of ordinary soda glasses (which absorb strongly at shorter wavelengths
than about 390 nm where the UV spectrum starts and visible violet light ends) and indeed almost all other types of glasses, along with perspex/lucite
and polycarbonate; with the sole exception of cut or fused quartz (as used in the cells of laboratory spectrophotometers).
This sort of instrument may be adaptable for measuring the intensities versus wavelengths of light transmitted by sunglasses: http://www.sciencemadness.org/scipics/spectroscope_2008.pdf
Even then, pure silica has some absorbance in the far UV; it is transparent to UV light only from a wavelength of about 180 nm through the whole of
the visible spectrum, and is of little use at shorter than 155 nm. There are doped (e.g. with Ce and other rare earth metal oxides) grades of fused
quartz which absorb only selected bands of UV light. A diffraction grating would probably be much better to use than a quartz prism, for UV light
diffraction and analysis, not being limited to wavelengths longer than about 155 nm.
See e.g. re UV tramsmittance of quartz used in optics of spectrometers:
http://en.wikipedia.org/wiki/Ultraviolet-visible_spectroscop...
http://en.wikipedia.org/wiki/Absorption_spectroscopy
http://www.chromatography-online.org/topics/quartz.html
http://www.quartz.com/gedata.html
http://www.mellesgriot.com/pdf/CatalogX/X_04_11-13.pdf
http://www.faqs.org/patents/app/20090188281
http://www.tianzhu.cn.net/csp/quartz/we2.htm
http://www.schott.com/advanced_optics/english/download/tie-3...
http://www.newrise-llc.com/fused-silica.html
http://cat.inist.fr/?aModele=afficheN&cpsidt=17443391
http://hktechco.com/en/bbs/shop/enlist.php?ca_id=10
http://www.ultraviolet.com/whatis.htm
Another possibility would be to use some sort of chemical detector of transmitted UV light through the sunglasses, which changes color on exposure
only to UV light, but this would not tell which wavelengths are transmitted and in what intensities.
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