 | | PROBLEM Next to the common reasons as direct sun light and high wattage of a light bulb, the biggest problem is CFL (Compact Fluorescent Licht). CFL is, in fact, a "folded" fluorescent lamp. Some of CFL’s give 500 time more UV-A then an old fashion light bulb! The UV-light is (invisible) generated in CFL lamp. This light is converted into the visible light with the help of special filter or coating inside the glass. - The composition and the thickness of the coating determine color and intensity of conversion of UV into the visible light.
- Glass absorbs UV light. A thicker glass allows less UV light.
- Amount of UV light is also influenced by wattage and construction of the bulb.
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 | | | Ø, cm | Wattage | Shape of lampshade | | 10 | 25w | Round | | 13 | 25w | Square | | 20 | 40w | Cylinder, square | | 20 | 25w | Rectangle | | 23 | 40w | Oval | | 25 | 40w | Cylinder, square | | 25 | 25w | Oval | | 28 | 40w | Cylinder, square, rectangle, drum | | 35 | 60w | Cylinder, square, rectangle, drum | | 35 | 40w | Oval | | 38 | 60w | Cylinder, square, | | 40 | 60w | Cylinder, square, | | 41 | 60w | Cylinder, square, rectangle, oval | | 41 | 40w | Slim oval, slim rectangle | | 46 | 60w | Cylinder, square, rectangle, drum, oval | | 46 | 100w | Short cylinder (empire), Short drum | | 51 | 60w | Slim straight oval | | 51 | 40w | Cylinder | | 56 | 100w | Short drum | |