Question

Calculate the focal length of a convex lens of radii of curvature 20cm and 25cm if if the refractive index of the lens is 1.6

Answer 1

using lens makers formula:

1/f=(u-1)(1/R1-1/R2)

1/f=(1.6-1)(1/20-(-1/25))

1/f=0.6(9/100)

1/f=0.6*0.09=0.054

f=1000/54=18.51cm