A cardsheet divided into squares each of size `1 mm^(2)` is being viewed at a distance of `9 cm` through a magnifying glass (a conerging lens of focal length `10 cm`) held close to the eye.
(a) What is the magnification produced by the lenas ? How much is the area of each square to the virtual image ?
(b) What is the angular magnification (magnifying power) of the lens ?
( c) Is the magnification in (a) equal to the magnifying power in (b) ? Explain

Explanation

(a) Here, area of each (object) square `= 1 mm^2, u = -9 cm, f = 10 cm`
As `(1)/(v)-(1)/(u)=(1)/(f) :. (1)/(v)=(1)/(f)+(1)/(u)=(1)/(10)-(1)/(9)=(9 - 10)/(90) = -(1)/(90)`
`v = -90 cm`
Magnification, `m = (v)/(|u|) = (90)/(9) = 10`
`:.` Area of each square in virtual image `=(10)^2 xx 1 = 100 sq. mm`
(b) Magnifying power `=(d)/(u) = (25)/(9) = 2.8`
( c) No, magnification in (a) which is (v/u) cannot be equal to magnifying power in (b) which is (d/u) unless `v = d` i.e., image is located at the least distance of distinct vision.