A stream of electrons from a heated filament was passed between two charged plates kept at a potential difference V esu. If e and m are charge and mass of an electron, respectively, then the value of h / $$\lambda $$ (where $$\lambda $$ is wavelength associated with electron wave) is given by :

Which of the following is the energy of a possible excited state of hydrogen?

The correct set of four quantum numbers for the valence elections of rubidium atom (Z= 37) is:

Energy of an electron is given by $$E = - 2.178 \times {10^{ - 18}}J\left( {{{{Z^2}} \over {{n^2}}}} \right)$$. Wavelength of light required to excite an electron in an hydrogen atom from level n = 1 to n = 2 will be
(h = 6.62 × 10⁻³⁴ Js and c = 3.0 × 10⁸ ms⁻¹)