The ratio of ground state energy of $Li^{2+}$,$He^{+}$,and $H$ is:

The work function of sodium metal is $4.41 \times 10^{-19} \ J$. If photons of wavelength $300 \ nm$ are incident on the metal,the kinetic energy of the ejected electrons will be $\left( \dots \right) \times 10^{-21} \ J$. (Given: $h = 6.63 \times 10^{-34} \ J \cdot s; c = 3 \times 10^{8} \ m/s$)

Energy of an electron is given by $E = -2.178 \times 10^{-18} \ J \left( \frac{Z^2}{n^2} \right)$. Wavelength of light required to excite an electron in a hydrogen atom from level $n = 1$ to $n = 2$ will be:

According to Bohr's atomic theory :-
$A$. Kinetic energy of electron is $\propto \frac{Z^{2}}{n^{2}}$.
$B$. The product of velocity $(v)$ of electron and principal quantum number $(n)$,'$vn$' $\propto Z^{2}$.
$C$. Frequency of revolution of electron in an orbit is $\propto \frac{Z^{3}}{n^{3}}$.
$D$. Coulombic force of attraction on the electron is $\propto \frac{Z^{3}}{n^{4}}$.
Choose the most appropriate answer from the options given below :

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

When light is directed at the metal surface,the emitted electrons