(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Hi, I have been reading this document ( chapter 1 )

http://pico.bo.astro.it/~massimo/pico/Teaching_files/ [Broken]

On page 21, equ 1.33 the it gives the following statement for finding the total deflection angle

˙"

The total deﬂection angle of the light path is now the integral over −e ( dot above )along the light

path.."

I understand pretty much everything up to this part.

2. Relevant equations

My question is why would the total deflection angle being found by the above integral? This makes no sense to me, either mathematically or physically - I admit i dont know any geometric optics.

3. The attempt at a solution

I tried to understand what the integral of "e dot" means ( in this case the tangent line ) but it just still doesn't help me understand how this will find the total deflection angle. Could someone help me understand whats going on?

Thanks:

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# Gravitational Lensing angles

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