An object 5.0 cm high is placed 2.0 cm from a converging (convex) lens which is being used as a magnifying glass. The image produced is 6.0 cm from the lens and is 15 cm high.What is the focal length of the lens?

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Answer 1 · 2018-03-13T16:27:27

#1.5cm#

We don't need the height of the object or image here.

From thin lens formula :-
#1/f=1/d_i+1/d_o#

#=>1/f=1/6+1/2#

LCM of 2 and 6 = 6

#=>1/f=1/6+3/6#

#=>1/f=(1+3)/6#

#=>1/f=(4)/6#

#=>f=6/4#

Flipping both sides,
#=>f=3/2#

#=>f=1.5cm#