A plano-convex lens (focal length f2 , refractive index , radius of curvature R ) fits exactly into a plano-concave lens ( focal length f1 , refractive index , radius of curvature R ) . Their plane surfaces are parallel to each other. Then , the focal length of the combination will be :
f1 + f2
f1 - f2
Lensmaker's Formula -
- wherein
refractive index of medium of object
refractive index of lens
are radius of curvature of two surface
and
f1 + f2
Option 3)f1 - f2
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