Calculate the radius of the fourth orbit of the $B^{4+}$ ion. (in $pm$)

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:

If the work function for the photoelectron emission of a metal is $3.75 \ eV$,then the threshold wavelength of the radiation needed for the ejection of the electron is approximately (in $nm$)

How did Niels Bohr obtain detailed information regarding the structure of atoms and molecules?

The series limit for the Balmer series of $H$ atom spectra is:

Explain linear and angular momentum.