JEE Main · 2015 · 04 Apr 2015 · Offline · Modern Physics

It helps to recall the energy bookkeeping of a hydrogen-like atom: the total energy obeys $E=-\mathrm{KE}$ and $\mathrm{PE}=2E$, so all three quantities are tied to the single number $E$. Dropping towards the ground state means falling into a more tightly bound level, so $E$ grows more negative and the total energy decreases. Because $\mathrm{PE}=2E$, the potential energy also becomes more negative, i.e. it decreases as well. But $\mathrm{KE}=-E$, so as $E$ falls the kinetic energy rises; the electron speeds up while both its potential and total energies drop.