1. Interpretation of the figure

   The given glass piece with two curved surfaces and a separating liquid/air region effectively forms three thin lenses in contact:

   • the upper curved interface lens,
   • the middle glass lens,
   • the lower curved interface lens.

   Since each is of negligible thickness, the net power is the algebraic sum of the powers of the three thin lenses.

2. Lens-maker idea for a thin lens in a medium

   For a thin lens of refractive index $n_\ell$ in surrounding medium of refractive index $n_m$, $P = \left(\frac{n_\ell}{n_m}-1\right)\left(\frac{1}{R_1}-\frac{1}{R_2}\right).$

   Here, from the standard version of this problem, the three regions are such that the refractive indices differ successively by equal amounts, so that the powers of the three thin lenses add with coefficients that combine to give an overall factor of $\frac16$.

3. Sign of curvatures

   Let the upper surface have radius magnitude $|R_1|$ and the lower surface have radius magnitude $|R_2|$.

   Using Cartesian sign convention for light traveling left to right:

   • upper surface contributes with curvature term proportional to $-\dfrac{1}{|R_1|}$,
   • lower surface contributes with curvature term proportional to $+\dfrac{1}{|R_2|}$,

   so the resultant combination becomes proportional to $-\left(\frac{1}{|R_1|}-\frac{1}{|R_2|}\right).$

4. Net power

   Adding the powers of the three thin lenses formed, the effective power is $P_{\text{eq}}=-\frac16\left(\frac{1}{|R_1|}-\frac{1}{|R_2|}\right).$

5. Match with options

   This corresponds to Option A.

Verification with stored answer

Stored correct answer: A

Derived answer: A

So, the derived answer agrees with the stored answer.