The wavelength of the second line of the Balmer series of a hydrogen atom is $\lambda \ nm$. What is the wavelength of the first line of the Lyman series of the $He^{+}$ ion (in $nm$)?

$A$ metal surface is illuminated by light of two different wavelengths $248 \ nm$ and $310 \ nm$. The maximum speeds of the photoelectrons corresponding to these wavelengths are $u_1$ and $u_2$ respectively. If the ratio $u_1 : u_2 = 2 : 1$ and $hc = 1240 \ eV \ nm$,the work function of the metal is nearly $:-$ (in $eV$)

Angular momentum of an electron in the $M$-shell of a $Li^{+2}$ ion is:

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

The ratio of the energy of the electrons in the ground state of hydrogen to the electrons in the first excited state of $Be^{3+}$ is:

The masses of photons corresponding to the first lines of Lyman and Balmer series of the spectrum of hydrogen atom are in the ratio of