A compound microscope uses an objective lens of focal length `4 cm` and eye lens of focal length `10 cm`. An object is placed at `6 cm` from the objective lens. Calculate magnifying power of compound microscope if final image is formed at the near point. Also, calculate length of the tube of compound microscope.

Answer

`7` ; `22 cm`

Explanation

Here, `f_(0) = 4 cm, f_(e) = 10 cm, u_(0) = - 6 cm`
From `(1)/(v_(0)) - (1)/(u_(0)) = (1)/(f_(0))`
`(1)/(v_(0)) = (1)/(f_(0)) + (1)/(u_(0)) = (1)/(4) - (1)/(6) = (1)/(12)`
`v_(0) = 12 cm`
`M = (v_(0))/(|u_(0)|)(1 + (d)/(f_(e))) = (12)/(6)(1 + (25)/(10)) = 7`
Length of microscope `= L = v_(0) + f_(e)`
`= 12 + 10 = 22 cm`