Question

The reflectance geometry of white-sky albedo can be represented as __________

• A. \( {bi-directional} \)
• B. \( {bi-conical} \)
• C. \( {bi-hemispherical} \)
• D. \( {directional-conical} \)

Hint:

White-sky albedo assumes completely diffuse illumination and is modeled using bi-hemispherical reflectance, where both illumination and reflection occur over hemispheres.

Answer 1

The Correct Option is C

White-sky albedo refers to the albedo calculated under the assumption of uniform diffuse illumination, such as from an overcast sky.
In this case, the incoming radiation is assumed to be isotropic, meaning it comes equally from all directions in the hemisphere above the surface.

To compute white-sky albedo, reflectance is integrated over all incoming directions in the upper hemisphere (diffuse illumination),
and the reflected radiation is also integrated over the entire hemisphere above the surface.
This corresponds to a bi-hemispherical reflectance geometry, where both the incoming and outgoing hemispheres are considered in the calculation.