The radii of curvature of both surfaces of a convex lens of focal length $f$ and focal power $P$ are equal. One of the surfaces is made plane by grinding. The new focal length and focal power of the lens are respectively:
- A$f/2, 2P$
- B$2f, P/2$
- C$\sqrt{2/f}, \sqrt{P/2}$
- D$2f/3, 2P/3$
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