Question

Which radiometric quantity represents power per unit area received from a surface per unit solid angle?

• A. Irradiance
• B. Radiance
• C. Radiant Flux
• D. Reflectance

Hint:

Important radiometric quantities: \[ \boxed{ \begin{aligned} \text{Radiant Flux} &\rightarrow \text{Power} \text{Irradiance} &\rightarrow \text{Power per unit area} \text{Radiance} &\rightarrow \text{Power per unit area per unit solid angle} \end{aligned} } \]

Answer 1

The Correct Option is B

Concept: Radiance is the amount of radiant power leaving or arriving at a surface per unit projected area per unit solid angle. It is the fundamental quantity measured by most remote sensing sensors.

Step 1: Recall the definition. Radiance is defined as \[ \boxed{ L= \frac{d^2\Phi} {dA\,d\Omega} } \] where
• \(\Phi\) = Radiant flux
• \(A\) = Area
• \(\Omega\) = Solid angle

Step 2: Identify the correct quantity. Thus, \[ \boxed{\text{Radiance}} \] represents power per unit area per unit solid angle. Therefore, the correct option is \[ \boxed{(B).} \]