It has much greater energy than visible radiation, but also much less power of penetration. Ultraviolet light is capable of initiating photochemical reactions, including fading of pigments, dyes, etc., and, being destructive to all organic matter, it can have a deleterious effect on such materials as paper and leather. Fortunately, its poor power of penetration (probably) reduces its likelihood of causing much damage, except on the surface of a material. Glass is opaque to ultraviolet light below 3300 A, and most other substances (quartz being a notable exception) below 2000 A. Exposure over a period of years, however, conceivably could be damaging; therefore, fluorescent lighting, which emits more ultraviolet radiation than does incandescent lighting, should be properly filtered with ultraviolet absorbing plastic panels. (143 , 198 , 235 )
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