A biconvex lens made of material with refractive index `n_(2)`. The radii of curvatures of its left surface and right surface are `R_(1)` and `R_(2)`. The media on its left and right have refreactive indices `n_(1)` and `n_(3)` respectively. The first and second focal lengths of the lens are respectively `f_(1)` and `f_(2)`.
The ratio, `f_(1)//f_(2)`, of the two focal lengths is equal to

Options

A. `n_(1)//n_(3)`
B. `(n_(1) - 1)//(n_(3) - 1)`
C. `(n_(1) + 1)//(n_(3) + 1)`
D. `(n_(2) -n_(3))//(n_(2) - n_(1))`

Answer

A