# reflectance derivations

1. reflectance from radiance and solar irradiance

   symbol | description | unit | variable name
   --- | --- | --- | ---
   \(\theta_{0}\) | solar zenith angle | \(deg\) | solar_zenith_angle {:}
   \(L\) | radiance | \(W/m2/sr\) | radiance {:}
   \(E\) | solar irradiance | \(W/m2\) | irradiance {:}
   \(R\) | reflectance | \(-\) | reflectance {:}

   The pattern : for the dimensions can represent {time}, or no dimensions at all.

   \[R = \frac{\pi L}{E\cos(\theta_{0})}\]

2. reflectance from wavelength radiance and wavelength solar irradiance

   symbol | description | unit | variable name
   --- | --- | --- | ---
   \(\theta_{0}\) | solar zenith angle | \(deg\) | solar_zenith_angle {:}
   \(L(\lambda)\) | radiance | \(W/m2/sr/m\) | wavelength_radiance {:}
   \(E(\lambda)\) | solar irradiance | \(W/m2/m\) | wavelength_irradiance {:}
   \(R\) | reflectance | \(-\) | reflectance {:}

   The pattern : for the dimensions can represent {time}, or no dimensions at all.

   \[R = \frac{\pi L(\lambda)}{E(\lambda)\cos(\theta_{0})}\]