For a hydrogen-like species,the ratio of velocities of electrons in the $I, II,$ and $III$ orbits,i.e.,$V_1 : V_2 : V_3$,will be:

First and second excitation potentials of hydrogen atom (in $eV$) would be respectively

Write down the postulates of Bohr's model for the hydrogen atom.

The threshold frequency $v_{0}$ for a metal is $7.0 \times 10^{14} \,s^{-1}.$ Calculate the kinetic energy of an electron emitted when radiation of frequency $v = 1.0 \times 10^{15} \,s^{-1}$ hits the metal.

If the ratio of energies of an electron in the excited states of $H$ and $Li^{2+}$ is $1: 9$,the radius ratio of the electron in the same excited states of $H$ and $Li^{2+}$ is

When electronic transition occurs from a higher energy state to a lower energy state with an energy difference equal to $\Delta E$ electron volts,the wavelength of the emitted line is approximately equal to