[11.1.5.2] In searchlighting: The point brilliance, E, from a distant light source depends on the inverse square law and the atmospheric transmittance according to:
E d^{2}=I (T_{1})^{d} ,
where:
E = the point brilliance
d = distance
I = intensity of the light source
T1 = atmospheric transmittance per unit distance, or transmissivity
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