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 ?
(A) K.E, P. E. and T.E. decreases
(B) K.E. increases but P. E. and T.E. decreases
(C) K.E. and T.E. decreases but P.E. increases
(D) K.E. decreases, P.E. increases but T.E. remains the same

The ratio of the density of oxygen nucleus $({}^{16}_{8}\text{O})$ and helium nucleus $({}^{4}_{2}\text{He})$ is

The force acting on the electron in hydrogen atom (Bohr's theory) is related to the principal quantum number n as

Using Bohr's atomic model, the orbital period of electron in hydrogen atom in the $n^{\text{th}}$ orbit is ($\epsilon_0$=permittivity of free space, h=Planck's constant, m = mass of electron, e = electronic charge)