Question

D).
To get a 12 cm focal length in a convex
lens made with a material having refrac
tive index 1.5 then curvature of radius is
A) 10 cm
C)3 cm
B) 6 cm
D) 12 cm​

Answer 1

Answer:

12 cm

Explanation:

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

taking r1=r2=r (Equi convex)

1/12=0.5*(1/r+1/r) [r1 and r2 have opposite signs]

1/12=0.5*2/r

1/12=1/r

r=12