1. Tardigrade
  2. Question
  3. Physics
  4. A double convex thin lens made of glass (refractive index μ=1.5 ) has both radii of curvature of magnitude 20 cm . Incident light rays parallel to the axis of the lens will converge at a distance L such that

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. A double convex thin lens made of glass (refractive index $\mu=1.5$ ) has both radii of curvature of magnitude $20\, cm .$ Incident light rays parallel to the axis of the lens will converge at a distance $L$ such that

Ray Optics and Optical Instruments

Solution:

$\frac{1}{f}=(\mu-1)\left(\frac{1}{R_{1}}-\frac{1}{R_{2}}\right)$
For double convex lens,
$\mu=1.5, R_{1}=+20 cm , R_{2}=-20$
$\frac{1}{f}=(1.5-1)\left(\frac{1}{(+20)}-\frac{1}{(-20)}\right)$
$\frac{1}{f}=0.5\left[\frac{2}{20}\right] \Rightarrow f=+20 cm$