IEVref:845-11-27ID:
Language:enStatus: Obsolete
Term: Allard's law
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Definition: law relating the illuminance E produced on a surface by a light source to the luminous intensity I of the source in the direction to the surface, to the distance d between the surface and the source, and to the atmospheric transmissivity T, which is assumed to be uniform; the surface is normal to the direction of the source and sufficiently distant for the source to be considered as a point source

E= I d 2 ⋅ T d/ d 0 MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadweacqGH9aqpdaWcaaqaaiaadMeaaeaacaWGKbWaaWbaaSqabeaacaaIYaaaaaaakiabgwSixlaadsfadaahaaWcbeqaamaalyaabaGaamizaaqaaiaadsgadaWgaaadbaGaaGimaaqabaaaaaaaaaa@3FF9@

where d0 is the length specified in the definition of T

NOTE 1 – The above formula is sometimes written

E= I d 2 ⋅ T d MathType@MTEF@5@5@+=feaagCart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHXgaruavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGeaGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaqFn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpeWZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadweacqGH9aqpdaWcaaqaaiaadMeaaeaacaWGKbWaaWbaaSqabeaacaaIYaaaaaaakiabgwSixlaadsfadaahaaWcbeqaaiaabsgaaaaaaa@3E11@

where the exponent d in Td is the numerical value of the distance d measured with d0 as "unit".

NOTE 2 – Taking into account the relationship given in 845-11-20 between T and the meteorological optical range ν, this law can also be written as

E= I d 2 ⋅ 0,05 d/v MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbbjxAHX garuavP1wzZbItLDhis9wBH5garmWu51MyVXgarqqtubsr4rNCHbGe aGqipG0dh9qqWrVepG0dbbL8F4rqqrVepeea0xe9LqFf0xc9q8qqaq Fn0lXdHiVcFbIOFHK8Feea0dXdar=Jb9hs0dXdHuk9fr=xfr=xfrpe WZqaaiqaciWacmGadaGadeaabaGaaqaaaOqaaiaadweacqGH9aqpda WcaaqaaiaadMeaaeaacaWGKbWaaWbaaSqabeaacaaIYaaaaaaakiab gwSixlaaicdacaGGUaGaaGimaiaaiwdadaahaaWcbeqaamaalyaaba GaamizaaqaaiaadAhaaaaaaaaa@4132@




Publication date:1987
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Internal notes:2017-06-02: Cleanup - Remove Attached Image 845-11-272.gif

2017-06-02: Cleanup - Remove Attached Image 845-11-273.gif

2017-06-02: Cleanup - Remove Attached Image 845-11-271.gif
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