1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Gravitational Lensing deflection angle question

  1. Jul 28, 2011 #1
    I wasn't sure whether this was the right place to post this since it isn't really coursework, but it seems like it could be.

    My problem is with the deflection angle of light for several point masses.

    The deflection for a point mass can be described as:

    [itex]\frac{4GM}{c^{2}\xi}[/itex]

    where [itex]\xi[/itex] is the minimum distance between the light and the lens.

    For a thin lens approximation of several point masses, the equation for the deflection angle is:

    [itex]\sum[/itex][itex]\frac{4Gm_{i}}{c^{2}}[/itex][itex]\frac{\xi-\xi_{i}}{|\xi-\xi_{i}|^{2}}[/itex]

    where [itex]\xi[/itex] is the position of the light ray in the lens plane and [itex]\xi_{i}[/itex] is the position of the mass [itex]m_{i}[/itex]. (they are vectors)

    It seems to me to be a direct extension of the point mass equation, but I don't understand where the [itex]\frac{\xi-\xi_{i}}{|\xi-\xi_{i}|^{2}}[/itex] comes from. It seems to me that it would just be [itex]\frac{1}{\xi-\xi_{i}}[/itex]. Can anyone explain it?
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted



Similar Discussions: Gravitational Lensing deflection angle question
  1. Gravitation question (Replies: 4)

  2. Gravitational Lensing (Replies: 2)

Loading...