Question 140 of 295
A bi-convex lens has radius of curvature of both the surfaces same as . If this lens is required to be replaced by another convex lens having different radii of curvatures on both sides , without any change in lens power then possible combination of and is :
Show answer and solution
Answer: (B) and
This will happen when
$\begin{aligned}
& \frac{1}{\mathrm{f}_1}=\frac{1}{\mathrm{f}_2} \\
& (\mu-1)\left(\frac{1}{\mathrm{R}_1}-\frac{1}{-\mathrm{R}_2}\right)=(\mu-1)\left(\frac{2}{\mathrm{R}}\right) \\
& \frac{1}{\mathrm{R}_1}+\frac{1}{\mathrm{R}_2}=\frac{2}{\mathrm{R}}
\end{aligned}$
$\begin{aligned}
& \frac{1}{\mathrm{f}_1}=\frac{1}{\mathrm{f}_2} \\
& (\mu-1)\left(\frac{1}{\mathrm{R}_1}-\frac{1}{-\mathrm{R}_2}\right)=(\mu-1)\left(\frac{2}{\mathrm{R}}\right) \\
& \frac{1}{\mathrm{R}_1}+\frac{1}{\mathrm{R}_2}=\frac{2}{\mathrm{R}}
\end{aligned}$
