A double convex lens of glass of refractive index `1.6` has its both surfaces of equal radii of curvature of `30 cm `each. An object of height `5 cm` is placed at a distance of `12.5 cm` from the lens. Calculate the size of the image formed.

Explanation

Here `mu=1.6,R_(1)=+30 cm,R_(2)=-30 cm`
`(1)/(f)=(mu-1)((1)/(R_(1))-(1)/(R_(2)))=(1.6-1)((1)/(30)+(1)/(30))=0.6xx(2)/(30)=(1)/(25)`
or `f=25 cm`
Using thin lens formula.
`(1)/(v)=(1)/(f)+(1)/(u)=(1)/(25)+(1)/(-12.5)=(1)/(25)`
or `v=-25 cm`
As `m=(h_(2))/(h_(1))=(v)/(u)` or `(h_(2))/(5 cm)=(-25)/(-12.5)` or `h_(2)=10 cm`
So a virtual image of height `10 cm` is formed at a distance of `25 cm` from the lens on the same side as the object.