The wavelength of a spectral line emitted is inversely proportional to:

The total energy of the electron of $H$ atom in the second quantum state is $-E_2$. The total energy of the $He^{+}$ ion in the third quantum state is

The electron in a hydrogen atom is in the first Bohr orbit $(n=1)$. The ratio of transition energies,$E(n=1 \rightarrow n=3)$ to $E(n=1 \rightarrow n=2)$,is

If $\lambda_0$ and $\lambda$ are the threshold wavelength and the wavelength of incident light,respectively,the velocity of the photoelectron ejected from the metal surface is:

The emission spectrum of a gaseous atom is line-based and not continuous. Why?

The shortest wavelength of $He^{+}$ ion in Balmer series is $x$. Then,the longest wavelength in the Paschen series of $Li^{2+}$ is: