A double convex lens has power


A double convex lens has power $P$ and same radii of curvature $R$ of both the surfaces. The radius of curvature of a surface of a plano-convex lens made of the same material with power $1.5 \mathrm{P}$ is:

  1. $\frac{\mathrm{R}}{2}$

  2. $2 \mathrm{R}$

  3. $\frac{3 R}{2}$

  4. $\frac{\mathrm{R}}{3}$

Correct Option: , 4



Power (P)

Refractive index is assume $\left(\mu_{\ell}\right)$



$\mathrm{P}^{\prime}=\frac{3}{2} \mathrm{P}$

$\left(\mu_{\ell}-1\right)\left(\frac{1}{R^{\prime}}\right)=\mu \frac{3}{2}\left(\mu_{\ell}-1\right)\left(\frac{2}{R}\right)$

$\therefore \quad \mathrm{R}^{\prime}=\frac{\mathrm{R}}{3}$


Leave a comment


Click here to get exam-ready with eSaral

For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.

Download Now