If the first ionization energy of $H$ atom is $13.6 \ eV,$ then the second ionization energy of $He$ atom is (in $eV$)

When $Z$ is doubled in an atom,which of the following statements are consistent with Bohr's theory?

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

What is the maximum wavelength line in the Lyman series of $He^{+}$ ion?

The $Bohr$ model of an atom could not account for:

When a metal surface is exposed to a certain frequency of electromagnetic radiation,the kinetic energy of the electron ejected from the metal surface is $0.20 \ eV$. If its work function $(W_0)$ is $4.80 \ eV$,the approximate frequency of the radiation falling on the metal surface in $Hz$ is: