The development of Radiative Transport Equation has a contribution term called the scattering phase density probability function. It account to scattering events from photons from a different solid angle direction that is scattered to the direction of interest.
∂u/∂t=-v∘∇u-v(μ_a+μ_s)u+∫〖vμ〗_s p_s (Ω^'→Ω)u(r,Ω^',t)ⅆΩ^'+q(r,Ω,t)
I am looking at the scattering phase density
∫〖vμ〗_s p_s (Ω^'→Ω)u(r,Ω^',t)ⅆΩ^'
After looking at the following source found the following plot of a Phase function
What troubles me is that this graph shows that the Phase function has magnitudes greater that 1. Is not a density probability function supposed to stay between 0 to 1?