Radii of curvature of a canverging lends are in the ration 1:2. Its focal length is 6cm and refractive index is 1:5. Then, its radii of curvature are…

Options

A. 9cm and 18cm
B. 6cm and 12cm
C. 3cm and 6cm
D. 4.5cm and 9cm

Answer

D

Explanation

Given `(R_(1))/(R_(2))=(1)/(2),f=6`cm and `mu=1.5`
Let, `R_(1)=R and R_(2)=2R`
We know that the focal length of converging lens by using releationg , `(1)/(f)=(mu-1)[(1)/(R_(1))-(1)/(R_(2))]`
Substituting all the values, we get
`R=4.5cm`
`R_(1)=4.5cm`
and `R_(2)=2xx4.5=9cm`