(i) At what distance should the lens be held from the card sheet in order to view the squares distinctly with the maximum possible magnifying power ?
(ii) What is the magnification in this case ?
(iii) Is the magnification equal to magnifying power in this case ? Explain.

Explanation

a) The maximum possible magnification is obtained when the image is formed at the near point (d=25cm).
Image distance, v=`-d=-25cm`.
Focal length, f=10cm
Object distance =u
According to the lens formula, we have:
`1/f=1/v-1/u`
`1/u=1/v-1/f`
`=1/-25-1/10=(-2-5)/(50)=-7/50`
`therefore u=-50/7=-7.14 cm`
Hence, to view the squares distinctly, the lens should be kept 7.14 cm away from them.
`|v/u|=25/(50//7)=3.5`
c) Magnifying power = Since the image is formed at the near point (25cm), the magnifying power is equal to the magnitude of magnification.