Emissivity

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

selfAdjoint

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

Bystander

"Anisotropic" for a point on a surface; integrate intensity at any point above an infinite plane surface, and it's isotropic.

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Callisto	Emissivity 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

selfAdjoint Recognitions: Gold Member Staff Emeritus	This cosine law is like the one for intensity of incoming solar radiation, and that's a cylinder, so I agree, anisotropic.

Bystander Recognitions: Gold Member Homework Help Science Advisor	"Anisotropic" for a point on a surface; integrate intensity at any point above an infinite plane surface, and it's isotropic.