Question

refractive index of convex lens is 1.5 when an object is at 30 cm image is at 20 cm use the lens formula and lens maker formula to find the focal length, and if, the radius of the curvature are equal find its value​

Answer 1

According to lens maker's formula,

 

f11=[n1(n2−n1)][R11−R21]

Here, f1 = 20 cm, n1 = 1(air) and n2 = 1.5

201=[1(1.5−1)][R11−R21]

201=(0.5)[R11−R21] ...(1)

Also,

f21=[n1(n

Answer 2

see the attachment for answers