KCET 2026 Physics Solved Paper

Concept:In the Bohr model of hydrogen, the total energy of the electron depends on the principal quantum number $n$.Moving to the ground state means $n$ decreases, which changes kinetic energy, potential energy, and total energy.Explanation:The total energy of an electron in the $n^{\text{th}}$ orbit is given by:$$E_n = -\frac{13.6}{n^2}\ \text{eV}$$For example, from $n=2$ to $n=1$:$$E_2 = -3.4\ \text{eV}$$$$E_1 = -13.6\ \text{eV}$$Since $E_1 < E_2$, the total energy becomes more negative, so total energy decreases.For a hydrogen atom, kinetic energy $K$ and potential energy $U$ are related to total energy $E$ as:$$K = -E$$$$U = 2E$$As $E$ decreases and becomes more negative:$K = -E$ increases.$U = 2E$ also becomes more negative, so it decreases.Therefore, kinetic energy increases, while both potential energy and total energy decrease.Answer:Option A: Its kinetic energy increases but potential energy and total energy decrease.