An angular magnification (magnifying power) of `30 X` is desired using an objective of focal length `1.25 cm` and an eye piece of focal length `5 cm`. How will you set up the compound microscope ?

Explanation

Assume microscope in normal use i.e., image at 25 cm. Angular magnification of the eye-piece
`=(25)/(5)+1=5`
Magnification of the objective
`=(30)/(6)=5`
`(1)/(5u_(o))-(1)/(u_(o))=(1)/(1.25)`
which gives `u_(0) = -1.5 cm, v_(0) = 7.5 cm. |u_(e)|= (25//6) cm = 4.17 cm`. The separation between the objective and the eye-piece should be `(7.5 + 4.17) cm = 11.67 cm`. Further the object should be placed 1.5 cm from the objective to obtain the desired magnification.