Physics · 2019
JEE Main · 12 January 2019, Shift 2 · Q22
A plano-convex lens (focal length f_2, refractive index μ_2, radius of curvature R) fits exactly into a plano-concave lens (focal length f_1,…
A plano-convex lens (focal length $\displaystyle f_2$, refractive index $\displaystyle \mu_2$, radius of curvature R) fits exactly into a plano-concave lens (focal length $\displaystyle f_1$, refractive index $\displaystyle \mu_1$, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be :
Official answer
(4)
$\displaystyle \frac{\mathrm{R}}{\mu_2-\mu_1}$
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JEE Main 2019 Physics question, with the answer from NTA’s final answer key. Where our answers come from.