The wave function of a molecular orbital formed by reinforce of wave functions of of atomic orbital A and B is represented as

When two atomic orbitals of A and B with the wave function of ${\Psi }_{\text{A}}\text{\hspace{0.17em}and\hspace{0.17em}}{\Psi }_{\text{B}}$ are combined to each other in a constructive interference (by addition mode) they form a molecular orbital as ${\psi }_{mo}={\psi }_{\text{A}}+{\psi }_{\text{B}}$ .

Destructible interference ${\Psi }_{\text{mo}}={\Psi }_{\text{A}}-{\Psi }_{\text{B}}$.