# Emissivity e varies with zenith angle according to e = E*cos(theta)

Callisto
If the emissivity e varies with zenith angle according to e = E*cos(theta) where E is the emissivity normal to the surface. Would this surface be an isotropic source of radiation?

Well, since e varies with angle then the flux density must vary accordingly so the surface would radiate anistropically.

Anybody disagree?
Callisto

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This cosine law is like the one for intensity of incoming solar radiation, and that's a cylinder, so I agree, anisotropic.