The energy of an electron in the first Bohr orbit of the $H$ atom is $-13.6 \, eV$. The energy value of an electron in the first excited state of the $H$ atom is ............ $eV$.

What is the difference in the line spectrum of different atoms compared to the hydrogen atom?

If the shortest wavelength of the $He^{+}$ ion in the Balmer series is $X \ m$,then the longest wavelength in the Paschen series of the $Li^{2+}$ ion is:

The work functions of two metals ($M_A$ and $M_B$) are in the $1:2$ ratio. When these metals are exposed to photons of energy $6 \ eV$, the kinetic energy of liberated electrons of $M_A:M_B$ is in the ratio of $2.642:1$. The work functions (in $eV$) of $M_A$ and $M_B$ are respectively.

Bohr's model can explain:

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