The energy (in $eV$) associated with the electron in the $1^{st}$ orbit of $Li^{2+}$ is

The number of absorption lines in the given figure will be .......

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

According to Bohr's principle,the relation between principal quantum number $(n)$ and the radius of the orbit $(r)$ is:

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

Which of the following corresponds to the energy of a possible excited state of hydrogen (in $eV$)?