Verified Solution • 2025–26 Session moderate

QNEET-2013-Ph-1497: NEET 2013 Physics - Class 12 NEET-2013-Ph-1497 Solution: A plano convex lens fits exactly into a plano concave lens.…

A plano convex lens fits exactly into a plano concave lens. Their plane surfaces are parallel to each other. If lenses are made of different materials of refractive indices μ1\mu_1 and μ2\mu_2 and R is the radius of curvature of the curved surface of the lenses then the focal length of the combination is (μ1−μ2)R(\mu_1-\mu_2)R 2R(μ2−μ1)\frac{2R}{(\mu_2-\mu_1)} R2(μ1+μ2)\frac{R}{2(\mu_1+\mu_2)} R2(μ1−μ2)\frac{R}{2(\mu_1-\mu_2)}

Multiple Choice Options

  • A R(μ1−μ2){R \over {\left( {{\mu _1} - {\mu _2}} \right)}} ( _ 1 _ _ _ 2 _ ) R _
  • B 2R(μ2−μ1){{2R} \over {\left( {{\mu _2} - {\mu _1}} \right)}} ( _ 2 _ _ _ 1 _ ) 2 R _
  • C R2(μ1+μ2){R \over {2\left( {{\mu _1} + {\mu _2}} \right)}} 2 ( _ 1 _ + _ 2 _ ) R _
  • D R2(μ1−μ2){R \over {2\left( {{\mu _1} - {\mu _2}} \right)}} 2 ( _ 1 _ _ _ 2 _ ) R _

Step-by-Step Verified Solution

Equivalent focal length is 1 f e q = 1 f 1 + 1 f 2 _ 1 f e q = ( _ 1 _ 1 ) ( 1 � _ 1 _ R ) + ( _ 2 _ 1 ) ( 1 _ R _ 1 � ) _ f eq = R ( _ 1 _ _ 2 )

Related Learning Resources & Exam Preparation

NEET PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring