Question

For a given optical system, the principal axis is x-axis and coordinates of object are `(-30,+1,0)` and coordinates of image are `(+20,-2,0)` All coordinates are in cm.
If the optical system is a convex lens, what is its focal length?
A. 12 cm
B. 10 cm
C. `100/3` cm
D. `100/9` cm

Answer 1

Correct Answer - D

`1/2=x/(50-x)Rightarrowx=50/3 Rightarrow50-x=100/3`
`(1)/(100/3)+1/(50/3)=1/f Rightarrowf=100/9` cm