Alec Aivazis added grav lense.tex  almost 10 years ago

Commit id: 891980020aaf9a6bdbef1056c3e23180ed45d672

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\section{Grav Lenses}  Diagram is in figure \ref{fig:gravlense}.  \begin{equation}  \theta D_{S} = \beta D_S + \alpha D_{LS}  \end{equation}  Because $b \approx \xi$ and $\xi \approx \theta D_L$ we can use the small angle approx. Therefore, $\theta = \beta + \frac{\theta_{E}^2}{\theta}$. Where  \begin{equation}  \theta_E = \left[ 2 R_S \frac{D_{LS}}{D_{S}D_{L}} \right] ^\frac{1}{2}  \end{equation}