Nancy T.

asked • 09/14/17

Focal length question

A converging glass lens (index of refraction 1.63) has a focal length of 40 cm in air. Find its focal length when it is immersed in a liquid, which has an index of refraction 1.32.
 
The way I set it up was...
 
The original equation: 1/f=(n-1)(1/r1-1/r2)
 
The (1/r1-1/r2) part of the equation stays constant so to "manipulate" the equation to solve for f2 when the lens is in the water...
 
f(liq)/f(lens) = (nlens-1)/(nliq-1)
x/40 cm = (1-1.63/(1-1.32)
x=78.75 cm 
 
I got the question wrong so I was wondering how to solve this problem correctly? 

1 Expert Answer

By:

Arturo O. answered • 09/15/17

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