; http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html#c1

(var N "number of scatterers")
(var alpha "polarizability")
(var R "distance from scatterer")
(var I_0 "original intensity")
(var I "scattered intensity")
(var lambda "wavelength of light")
(var Theta "angle of scattering")

(eq I
    (* I_0
        (/ (* 8 (exp pi 4) N (exp alpha 2))
           (* (exp lambda 4) (exp R 2)))
        (+ 1 ((exp cos 2) Theta))))