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![[Post New]](/templates/default/images/icon_minipost_new.gif) 24 Mar 2008 20:31:26 IST
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SI photometry units | Quantity | Symbol | SI unit | Abbr. | Notes | | Luminous energy | Qv | lumen second | lm·s | units are sometimes called talbots | | Luminous flux | F | lumen (= cd·sr) | lm | also called luminous power | | Luminous intensity | Iv | candela (= lm/sr) | cd | an SI base unit | | Luminance | Lv | candela per square metre | cd/m2 | units are sometimes called nits | | Illuminance | Ev | lux (= lm/m2) | lx | Used for light incident on a surface | | Luminous emittance | Mv | lux (= lm/m2) | lx | Used for light emitted from a surface | | Luminous efficacy | | lumen per watt | lm/W | ratio of luminous flux to radiant flux; maximum possible is 683.002 lm/W |
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The Scientist does not study nature because it is useful; he studies it because he delights in it, & he delights in it because it is beautiful. If nature were not beautiful, it would not be worth knowing, life would not be worth living. Ofcourse I do not here speak of that beauty that strikes the senses, the beauty of qualities & appearances; not that I undervalue such beauty, far from it, but it has nothing to do with science; I mean that profounder beauty which comes from the harmoniuos order of the parts, & which a pure intelligence can grasp. |
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