An angular magnification (magnifying power) of 30X is desired using an objective of focal length 1.25cm and an eyepiece of focal length 5cm. 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.