NEET-XII-Physics
qstns with ansrs year:2022
- #22A biconvex lens has radii of curvature, `` 20\, cm `` each. If the refractive index of the material of the lens is `` 1.5 `` , the power of the lens is :
(A)infinity
(B) `` +2 D ``
(C) `` +20 D ``
(D) `` +5 D ``digAnsr: DAns : `` R _{1}= R _{2}=20\, cm =0.2\, m ``
`` \mu=\frac{3}{2} ``
`` P =\frac{1}{ f }=(\mu-1)\left(\frac{1}{ R _{1}}-\frac{1}{ R _{2}}\right) ``
`` P =\left(\frac{3}{2}-1\right)\left(\frac{1}{0.2}+\frac{1}{0.2}\right) ``
`` P =\frac{1}{2}\left(\frac{2}{0.2}\right)=\frac{10}{2}=+5 D ``