A graph sheet divided into squares each of size 1mm^2 is kept at distance of 7cm from a magnifying glass of focal length of 8cm. The graph sheet is viewed through the magnifying lens keeping the eye close to the lens. Find (i) the magnification produced by the lens (ii) the area of each square in the image formed (iii) the magnifying power of the magnifying lens. Why is the magnification found in (i) different from the magnifying power?

A graph sheet divided into squares each of size 1mm^2 is kept at dista

1.	A graph sheet divided into squares each of size 1mm^2 is kept at distance of 7cm from a magnifying glass of focal length of 8cm. The graph sheet is viewed through the magnifying lens keeping the eye close to the lens. Find (i) the magnification produced by the lens (ii) the area of each square in the image formed (iii) the magnifying power of the magnifying lens. Why is the magnification found in (i) different from the magnifying power?
Answer» Solution :(i) `u=-7cm, f=+8cm, v=?` For a lens `1/f=1/v=1/u` `1/(+8)=1/v-1/(-7)=1/8-1/7=1/56, v=-56cm` Magnification `M=v/u=(-56)/(-7)=+8` (ii) Each square is of size `1mm^1` I.e its length and BREADTH are each to 1mm. The virtual image formed has LINEAR magnification 8. So its length and breadth are each equal to 8mm. The area of the image of each square= `8 times 8 mm^2=64mm^2` (iii) Magnifying power of the magnifying glass i.e., simple microscope `m=1+D/f=1+25/8=4.125 (THEREFORE D=25cm)` the magnification FOUND in (i) is different from the magnifying power because the image DISTANCE in (i) is different from the least distance of distinct vision, D.