About radiance equation in Radiometry

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SUMMARY

The discussion centers on the radiance equation in radiometry, specifically the formula L = d²P / (dA * cos(a) * dw), where L represents radiance, P denotes power flux, A*cos(a) indicates the projected area, and w is the solid angle. The inquiry focuses on the presence of the second derivative d²P in the formula. It is clarified that radiance is defined as power per unit area per solid angle, leading to a better understanding of the equation's components.

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  • Understanding of radiometry concepts
  • Familiarity with differential calculus
  • Knowledge of solid angles and projected areas
  • Basic principles of power flux in physics
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  • Research the derivation of the radiance equation in detail
  • Explore applications of radiance in optical engineering
  • Study the relationship between power flux and area in radiometry
  • Learn about the implications of solid angles in radiative transfer
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dammage
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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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Because radiance is power per unit area, per solid angle.
 
Ah, I understand now. Thank you !
 

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