If two thin lenses are kept coaxially together, then their power is proportonal `(R_(1),R_(2) "being the radii of curved surfaces")` to

Options

A. `R_(1) + R_(2)`
B. `[(R_(1) + R_(2))/(R_(1)R_(2))]`
C. `[(R_(1)R_(2))/(R_(1)R_(2))]`
D. none of these

Answer

A, B

Explanation

`P=(1)/(f_(1))+(1)/(f_(2))=(2)/(R_(1))+(2)/(R_(2))=2((R_(1)+R_(2))/(R_(1)R_(2)))orp approx ((R_(1)+R_(2))/(R_(1)R_(2)))`