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4.5: Mean Specific Intensity

  • Page ID
    6668
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    Look around you again from your position somewhere in the middle of a stellar atmosphere. The specific intensity around you is not isotropic. It is quite large in the sky above you, but is much greater if you look towards the hell at your feet. The mean specific intensity \(J\) around the complete \(4\pi\) steradians around you is

    \[J = \frac{1}{4\pi} \int_0^{2\pi} \int_0^\pi I (\theta) \sin \theta \ d \theta d\phi \label{4.5.1}\]

    or, for short

    \[J = \frac{1}{4\pi} \int I d \omega . \label{4.5.2}\]

    At the centre of the star, where the specific intensity is isotropic, \(J = I\).


    This page titled 4.5: Mean Specific Intensity is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Jeremy Tatum via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.

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