- #1
icedragon
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Homework Statement
Hi all. This is a problem from one of the problem sheets from earlier in the term. I'm just revising for my exam tomorrow and can't solve this one. Here it is:
Consider a light source placed at a fixed distance L from a screen, such that a lens of focal length
f can be placed between the source and the screen. Show that as long as f < fmax there are two
positions where the lens can be placed so that an image is formed on the screen, and find a value for fmax.
Homework Equations
1/s + 1/s' = 1/f
The Attempt at a Solution
I substituted in s' = L-s which gives me:
1/s + 1/(L-s) = 1/f
Given that there are two solutions and the nature of that formula I am guessing I need a quadratic equation and then to solve for s. Not sure how to expand that equation so I can solve for s?
Thanks