Question

if the radius of curvature of a convex lens are both 20 cm and the refractive index of glass of lens is 1.5 of the focal length of the lens will be

a 10 cm

b 20 cm

c 22

d 40 cm​

Answer 1

From Lens makers formula, f1=(μ−1)(R11−R21)

R1=∞

R2=−20 cm

f1=(1.5−1)(201)

f=40cm