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girlinphysics
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Homework Statement
A thin lens is placed 2m after the beam waist. The lens has f = 200mm. Find the appropriate system matrix.
This is a past exam question I want to check I got right.
Homework Equations
For some straight section [[1 , d],[0 , 1]] and for a thin lens [[1 , 0],[-1/f , 1]]
The Attempt at a Solution
[[r2],[r2']] = [[1 , d],[0 , 1]] [[1 , 0],[-1/f , 1]] [[r1],[r1']]
I multiplied the two matrices and found [[1-d/f, d] , [-1/f , 1]]
Is this correct? Or am I meant to add an additional straight section after the lens? I get confused as to when to use the straight section matrix. Thanks.