When an electron jumps from $L$ to $K$ shell,what happens to the energy?

Four lowest energy levels of $H$-atom are shown in the figure. The number of emission lines could be obtained by transitions from these levels. The total number of possible emission lines is:

$A$ single-electron species has a nuclear charge of $+Ze$,where $Z$ is a constant. The energy required to excite an electron from the $2^{nd}$ Bohr orbit to the $3^{rd}$ Bohr orbit is $47.2 \ eV$. Calculate the value of $Z$.

The velocity of an electron in the $3^{rd}$ excited state of $Be^{3+}$ is .......

Calculate the wavenumber of the photon emitted during transition from the orbit of $n=2$ to $n=1$ in a hydrogen atom. $[R_H = 109677 \ cm^{-1}]$ (in $cm^{-1}$)

When an electron makes a transition from $(n+1)$ state to $n^{th}$ state,the frequency of emitted radiation is related to $n$ according to $(n >> 1)$: