Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

  1. Aug 19, 2005 #1
    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?
  2. jcsd
  3. Aug 20, 2005 #2


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    This cosine law is like the one for intensity of incoming solar radiation, and that's a cylinder, so I agree, anisotropic.
  4. Aug 20, 2005 #3


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    "Anisotropic" for a point on a surface; integrate intensity at any point above an infinite plane surface, and it's isotropic.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook