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1. |
A Plano-convex lens (focal length f2 refractive index μ2 radius of curvature R) fits exactly into a plano-concave lens (focal length f1, refractive index μ1, radius of curvature R). Their plane surfaces are parallel to each other. Then, the focal length of the combination will be |
A. | f1 – f2 |
B. | \(\frac{{\rm{R}}}{{{{\rm{\mu }}_2} - {{\rm{\mu }}_1}}}\) |
C. | f1 + f2 |
D. | \(\frac{{2{{\rm{f}}_1}{{\rm{f}}_2}}}{{{{\rm{f}}_1} + {{\rm{f}}_2}}}\) |
Answer» C. f1 + f2 | |