Question

. a convex lens is in contact with concave lens. the magnitude of the ratio of their focal length is 2 . 3 their equivalent focal length is 30 cm. what are their individual focal lengths (in cm).

Answer 1

Hiiii....

Let F be equivalent focal lenght....

1/F = 1/ f1 + 1/ f2 .......

f1 / f2 = 2 / 3 ....(1) ...

1/30 = 1/f1 + 1/f2 ..... (2)..

f1 = 50 and f2 = 75 .....