For simplicity, let's take the 1D Schrödinger's equation for a single non-relativistic particle: $$-\frac{\hbar^2}{2m} \frac{\partial^2 \Psi(x,t)}{\partial x^2} + V(x) \Psi(x,t) = i\hbar \frac{\partial\Psi(x,t)}{\partial t}$$ Applying separation of variables, $\Psi(x,t)=\psi (x)\phi (t)$, we get...

It is said that the spectral lines of a particular atom or molecule is unique and this could be used to identify the substance by comparing the spectrum with the existing library of spectra of different atoms, molecules and compounds. In other words, spectral lines are like the fingerprints which...

How do we know that the quanta of a quantized Dirac field describe elementary spin-1/2 fermions (or point particles of spin-1/2) and not composite spin-1/2 fermions (or extended structure of spin-1/2) such as a proton or a neutron? Response to comment Surely Dirac equation doesn't describe the c...