Imagine that the mean solar irradiance reaching the earth falls on a high altitude, low-latitude fresh snow field that acts as a perfect lambertian reflector. It has albedo of 100% with radiance being reflected isotropically into the upward hemisphere. Assume that you can completely ignore atmospheric effects, that the snow field is horizontal and that the solar zenith angle is 0. What would the reflected radiance be? ** What i have tried is: I know how to find the solar irradiance and also i have the formula for finding the reflected radiance but there is this thing called the BRDF (bidirectional reflectance distribution function) which i am not totally sure about. i tried using: L(p, ωr ) = f(p, ωi , ωr ) E(p, ωi ) = f(p, ωi , ωr ) L(p, ωi ) cosΘi dωi where The BRDF is f(p, ωi , ωr ) and the other function is the irradiance. Dont know where to go from here to find the Reflected radiance.