deletions | additions       diff --git a/Orbits of a Photon.tex b/Orbits of a Photon.tex  index c250868..761ccf4 100644  --- a/Orbits of a Photon.tex  +++ b/Orbits of a Photon.tex 
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are conserved quantities along the path of the photon.   setting $u \cdot u = 0$ since its a light ray gets with $\theta = \frac{\pi}{2}$ gives  \begin{equation}  \begin{split}  u \cdot u = g_{\alpha \beta} \frac{d x^\alpha}{d \lambda}\frac{d x^\alpha}{d \lambda} \\  \frac{1}{b^2} = \frac{1}{l^2}\left( \frac{dr}{\lambda}\right)^2 + W_{\rm{eff}}(r)  \end{split}  \end{equation}  where  \begin{equation}  \begin{split}  b^2 &= \frac{l^2}{e^2} \\