The first quantum mechanical model of the atom was proposed by ........

$A$ bulb emits light of wavelength $4500 \ \mathring{A}$. The bulb is rated at $150 \ \text{W}$ and $8\%$ of the energy is emitted as light. How many photons are emitted by the bulb per second?

Henry Moseley studied the characteristic $X$-ray spectra of elements. The graph which represents his observation correctly is: (Given $\nu =$ frequency of $X$-ray emitted; $Z =$ atomic number)

In the transition of an electron in an atom,its kinetic energy changes from $y$ to $y/4$. The change in potential energy $(P.E.)$ will be:

The energy of the second Bohr orbit of the hydrogen atom is $-328 \ kJ \ mol^{-1}$. Hence,the energy of the fourth Bohr orbit would be .............. $kJ \ mol^{-1}$.

Which of the following electronic transitions in a hydrogen atom results in the emission of a spectral line with the shortest wavelength?