The element used by Rutherford in his famous scattering experiment was

For a $H$ atom,the wavelength for the highest energy transition is $91.2 \ nm$. Calculate the corresponding wavelength for $He^{+}$ in $nm$.

Give the Rydberg equation for all lines in the hydrogen spectrum.

The work function of a metal $M$ is $6.3 \ eV$. The wavelength of the incident radiation required to just eject the electrons from its surface (in $nm$) is

Calculate the energy released when an electron in a hydrogen atom transitions from the $3^{rd}$ energy level to the $2^{nd}$ energy level.

The ratio of the radii of the first three Bohr orbits is: