Question

Focal length of Plano convex lens is ________ when it's radius of curvature of the surface is R and n is the refractive index of the lens? What is the relation between R and n to find out focal length? ​

Answer 1

Answer

Given focal length f=Rf=R where R= radius of curvature.------(1)

We know,

\dfrac{1}{f}=\dfrac{\mu-1}{R}  

f

1

​  

=  

R

μ−1

​  

 for plano-convex lens

Put the value of F from equ 1

\dfrac{1}{f}=\dfrac{\mu-1}{F}  

f

1

​  

=  

F

μ−1

​  

 

1=\mu-11=μ−1

\mu=2μ=2