The relativistic equation derived for Schwarzschild coordinates is d 2 u d θ θ 2 + u = r s c 2 2 h 2 + 3 r s 2 u 2 where c is the speed of light and r s is the Schwarzschild radius. And for Reissner–Nordström metric we will obtain d 2 u d θ θ 2 + u = r s c 2 2 h 2 + 3 r s 2 u 2 − − G Q 2 4 π π ε ε 0 c 4 ( c 2 h 2 u + 2 u 3 ) where Q is the electric charge and ε ε 0 is the vacuum permittivity.