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 :

Options

A. `R/(mu_1-mu_2)`
B. `(2R)/(mu_1-mu_2)`
C. `R/(2(mu_1-mu_2))`
D. `R/(2-(mu_1-mu_2))`

Answer

A