Luminous intensity due to an isotropic point source of light

  1. Does the luminous intensity due to an isotropic point source of light at a point on a surface depend on the angle it makes with the normal to the surface?
     
  2. jcsd
  3. HallsofIvy

    HallsofIvy 40,314
    Staff Emeritus
    Science Advisor

    Your question is a bit confusing. If you mean the intensity as measured AT the point on the surface, then no, it does not depend on the angle it makes with the normal. In fact, if you removed the surface entirely, it would not change the intensity at that point. If you mean the intensity at some point off the circle due to the reflection of the light from the surface, then yes, it does depend on the angle as well as the angle the line from your eye makes with the surface. There will be two kinds of reflection: specular reflection, especially strong from a mirror or metal surface, that depends strongly on the angle, and diffuse reflection, more important if you have a "matte" surface that depends primarily on the type of surface but not the angle.
     
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