An electron makes a transition from an excited state to the ground state of a hydrogen like atom. Out of the following statements which one is correct?

If the horizontal velocity given to a satellite is greater than critical velocity but less than the escape velocity at the height, then the satellite will

Two identical springs of constant '$$\mathrm{K}$$' are connected in series and parallel in shown in figure. A mass '$$\mathrm{M}$$' is suspended from them. The ratio of their frequencies is series to parallel combination will be

The radii of curvature of both the surfaces of a convex lens of focal length '$$\mathrm{f}$$' and focal power '$$\mathrm{P}$$' are equal. One of the surfaces is made plane by grinding. The new focal length and focal power of the lens is respectively