A compound microscope has an objective of focal length 1 cm and an eyepiece of focal length 2.5 cm. An object has to be placed at a distance of 1.2 cm away from the objective for normal adjustment. a.Find the angular magnification. b.Find the length of the microscope tube.

Explanation

Using lens equation for the objective,
`(1)/(v)-(1)/(u)=(1)/(f)`
`(1)/(v_(0))-(1)/((-1.2cm))=(1)/((1cm))`
`impliesv_(0)=6cm`.
`M_("far point")=-((v_(0))/(u_(0)))((D)/(f_(e)))=-((6cm)/(1.2 cm))((25 cm)/(2.5 cm))=-50`
(b) For far point adjustment, the first image formed by the objective should be formed at the focal length of the eye-piece.
`impliesL=v_(0)+f_(e)=6cm+2.5cm=8.5 cm`.