(a) An object is seen through a simple microscope of focal length `12cm`. Find the angular magnification produced if the image is formed at the near point of the eye which is `25cm` away from it.
(b) A `10D` lens is used as a magnifier. Where should the object be placed to obtain maximum angular magnification for a normal eye (near point `= 25cm)`?

Explanation

Maximum angular magnification is achieved when the fiN/Al image is formed at the near point. Thus, `v=-25cm. The focal length is `f=1/10 m=10 cm.`
We have
`1/v-1/u=1/f`
`or -1/(25cm)-1/u=1/(10cm)`
or `1/u=-1/(25cm)-1/(10cm)`
`or u=-50/7cm=-7.1cm`