The energy of an electron in the $3^{rd}$ orbit of $H$-atom (in $J$) is approximately:

The kinetic energy of an electron is $5.65 \times 10^{-25} \ J$. Find the frequency of the electron.

Bohr’s atomic theory gave the idea of :

What is the experimental evidence in support of the idea that electronic energies in an atom are quantized?

$A$ photon of wavelength $3000 \ \mathring{A}$ strikes a metal surface. The work function of the metal is $2.13 \ eV$. What is the kinetic energy of the emitted photoelectron (in $eV$)? $\left(h=6.626 \times 10^{-34} \ J \ s\right)$

If the wave number of radiation emitted for the electron transition from an excited state to ground state of hydrogen is $\frac{5x}{36} \ m^{-1}$,the wave number of radiation absorbed for the electron transition from the above excited state to the next immediate excited state in $m^{-1}$ is: