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

An optical system consists of two identical lenses; the focal length of each lens is f_{o}(where f_{o}) is positive). The lenses are separted by a distance d. Denote the focal lenths of the lens assembly by f and f'.

a) Show that for any separation of the lenses f = f'

b) Find the separation between lenses that leads to the focal length of the lens assembly being equal to 2f_{o}

2. Relevant equations

thin lens equations, refracting/travelling matrices?, f' = -1/a_{21}

3. The attempt at a solution

a) I did the intuitive approach: a set of rays coming from either end of the 2 lense assembly will experience the same assembly, and hence converge to the same focal lengths (after exiting assembly at either end)

b) I used the matrix method with the matrix for thin lense being (1, 0; -1/f_{o}, 1)

anyways, after some calculation... I got: d = (3/2)f_{o}(correct?)

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# Homework Help: Two Thin Lenses

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