A simple microscope is a combination of two leses of powers `+ 15 D and + 5 D` in contact. Calculate magnifying power of microscope, if final image is formed at `25 cm` from the eye.

Explanation

Here, `P = P_1 + P_2 = 15 + 5 = 20 D`
Focal length of combination,
`f = (100)/(P) = (100)/(20) = 5 cm`
Magnifying power, `m = 1 + (d)/(f) = 1 + (25)/(5) = 6`.