Question

1)
9. Find the radii of curvature of a convexo-concave convergent lens made of glass with
refractive index n=1,5 having focal length of 24cm. One of the radii of
curvature is double the other. (Ans: R = 6cm, R = 12cm) (AS)
2​

Answer 1

Answer:

Given: a convexo-concave convergent lens made of pf glass with refractive index, ν=1.5 and focal length, f=24cm. It has one of the radii of curvature is double the other

To find its radii of the curvature

Solution:

According to the given criteria,

R1=2R2

for convexo-concave lens R1 is positive and R2 is positive

According to the lens maker formula,

f1=(n−1)(R11−R21)⟹241=(1.5−1)(R11−2R11)⟹24×0.51=2R12−1⟹R1=212=6cm

∴,R2=2R1=12cm

Hence the radii of the curvature is 6cm and 12cm