| One plano-convex and one plano-concave lens of same radius of curvature 'R' but of different materials are joined side by side as shown in the figure. If the refractive index of the material of 1 is \[{{\mu }_{1}}\]and that of 2 is \[{{\mu }_{2}}\], then the focal length of the combination is : [JEE Main 10-4-2019 Morning] |
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A) \[\frac{R}{2-({{\mu }_{1}}-{{\mu }_{2}})}\]
B) \[\frac{2R}{({{\mu }_{1}}-{{\mu }_{2}})}\]
C) \[\frac{R}{2({{\mu }_{1}}-{{\mu }_{2}})}\]
D) \[\frac{R}{{{\mu }_{1}}-{{\mu }_{2}}}\]
Correct Answer: D
Solution :
[d] For 1st lens |
for 2nd lens |
 |
 |
Hence  |
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