# Why Majorana neutrinos is a solution for the existence of only LH neutrinos?

At lesson my teacher stated that the possible reason for why only LH neutrinos are observed are that either: neutrinos are Dirac fermion but the RH neutrinos are not interacting weakly or that they are Majorana fermion ($\Psi=\Psi^{\star}$) but he didn't explain why this second solution solves the issue, he only wrote $\Psi=(\Psi_L, i\sigma_2\Psi_L^\star)$ but not how to reach this (if this is true I understand why we do not find RH neutrinos). Can anybody help me clarify this point?