The length of the compound microscope is `14 cm.` The magnifying power for relaxed eye is `25`. If the focal length of eye lens is `5 cm`, then the object distance for objective lens will be

Options

A. 1.8 cm
B. 1.5 cm
C. 2.1 cm
D. 2.4 cm

Answer

A

Explanation

(a) Length of compound microscope,
`L_(oo)=v_(0)+f_(e)rArr14=v_(0)+5`
`therefore` `v_(0)=9 cm`
Magnifying power of microscope for relaxed eye
`M=v_(0)/u_(0)cdotD/(f_(e)) or25=9/u_(0)cdot25/5`
or distant of object, `u_(0)=9/5=1.8 cm`