Question

Graph of position of image vs position of point object from a convex lens is shown. Then, focal length of the lens is

A. `0.50 pm 0.05 cm`
B. `0.50 pm 0.10 cm`
C. `5.00 pm 0.05 cm`
D. `5.00 pm 0.10 cm`

Answer 1

Correct Answer - C
From `(1)/(f)=(1)/(v)-(1)/(u)=(1)/(10)-(1)/(-10)=(1)/(5)rArr f=5cm`
From graph `Delta u = 0.1 cm, Delta v = 0.1 cm`
But `(Deltaf)/(f^(2))=(Deltav)/(v^(2))+(Deltau)/(u^(2))`
so `Deltaf=((0.1)/(100)+(0.1)/(100))(25)=0.05`
`rArrf = (5 pm 0.05)cm`