In the Bohr model of the atom,when an electron undergoes a transition from $n = 1$ to $n = 3$,the energy absorbed or emitted is ........

In the transition of an electron in an atom,its kinetic energy changes from $y$ to $y/4$. The change in potential energy $(P.E.)$ will be:

How many emission spectral lines are possible when a hydrogen atom is excited to the $n$th energy level?

When an electron moves from $L$-shell to $M$-shell,then it will be accompanied by :

What transition in the hydrogen spectrum has the same wavelength as the Balmer transition,$n=4$ to $n=2$,of the $He^{+}$ spectrum?

The work function of sodium metal is $4.41 \times 10^{-19} \ J$. If photons of wavelength $300 \ nm$ are incident on the metal,the kinetic energy of the ejected electrons will be $\left( \dots \right) \times 10^{-21} \ J$. (Given: $h = 6.63 \times 10^{-34} \ J \cdot s; c = 3 \times 10^{8} \ m/s$)