About radiance equation in Radiometry

Thread starter dammage
Start date Jun 6, 2011
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Radiance Radiometry

AI Thread Summary

The discussion centers on the radiance equation in radiometry, specifically the formula L = d2P / (dA*cos(a)*dw), where L represents radiance, P is power flux, A*cos(a) is the projected area, and w is the solid angle. A key point raised is the use of the second derivative of power, d2P, in the equation. The clarification provided indicates that radiance is defined as power per unit area per solid angle, which helps in understanding the necessity of the second derivative. The conversation concludes with an acknowledgment of the explanation, indicating a resolution to the initial confusion. Understanding the relationship between these variables is crucial for accurate calculations in radiometry.

Jun 6, 2011

dammage

Homework Statement

According to some pages on web, differential formula for calculating radiance L is :

L = d²P / ( dA*cos(a)*dw)

L : radiance
P : power flux
A*cos(a) : projected area
w : solid angle

Please tell me why does power P has derivaties two times d²P ?

Homework Equations

The Attempt at a Solution

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Jun 6, 2011

ideasrule

Homework Helper

Because radiance is power per unit area, per solid angle.

Jun 20, 2011

dammage

Ah, I understand now. Thank you !

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