If the wavelength of the first line of the Balmer series is $656.1 \ nm$,then the wavelength of the second line of this series will be ............. $nm$.

If the work function of a metal is $6.63 \times 10^{-19} \ J$,the maximum wavelength of the photon required to remove a photoelectron from the metal is $.... \ nm$. (Nearest integer)
[Given : $h = 6.63 \times 10^{-34} \ J \ s$,and $c = 3 \times 10^{8} \ m \ s^{-1}$ ]

$A$ surface ejects electrons when hit by green light but not when hit by yellow light. Will electrons be ejected if the surface is hit by red light?

The radius of the $2^{nd}$ orbit of $B^{4+}$ ion is:

The ratio of the lowest energy in terms of wave numbers of the Balmer and Lyman series of lines of the atomic spectrum of hydrogen is

What is the separation energy (in $eV$) for $Be^{3+}$ in the first excited state?