| Lambert's law for a surface element whose radiance or luminance is the same in all directions of the hemisphere above the surface Note 1 to entry: Lambert's cosine law can be expressed by I(θ) = In cos θ where I(θ) and In are the radiant intensities or luminous intensities of the surface element in a direction at an angle, θ, from the normal to the surface and in the direction of that normal, respectively. Note 2 to entry: This entry was numbered 845-04-56 in IEC 60050-845:1987.
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