17-608

irradiance (at a point of a surface) [Ee]

1. quotient of the radiant flux dΦe incident on an element of the surface containing the point, by the area dA of that element

2. equivalent definition: integral, taken over the hemisphere visible from the given point, of the expression LecosθdΩ, where Le is the radiance at the given point in the various directions of the incident elementary beams of solid angle dΩ, and θ is the angle between any of these beams and the normal to the surface at the given point

        

Unit: W⋅m-2

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