Question

What is the focal length of a double convex
lens for which radius of curvature of the
surface is 40 cm (*u, = 1.5)?
(A) 50 cm
(B) 40 cm
(C) -30 cm
(D) -40 cm​

Answer 1

Answer:

1/f=(n-1)(1/r1-r2),r2=-1r1

1/f=(1.5-1)(1/40+1/40)

=0.5*2/40

1/f=0.025

f=40