Why Study Perturbation Theory?

Perturbation theory is an important tool for describing real quantum systems, as it turns out to be very difficult to find exact solutions to the Schrödinger equation for Hamiltonians of even moderate complexity.

Why do we use perturbation theory?

There is a general method of calculating these errors; it is called perturbation theory. One of the most important applications of perturbation theory is to calculate the probability of a transition between states of a continuous spectrum under the action of a constant (time-independent) perturbation.

What is the role of perturbation to energy state?

The task of perturbation theory is to approximate the energies and wavefunctions of the perturbed system by calculating corrections up to a given order. expressions (3) and (4) for the Hamiltonian and wavefunction respectively. as this is sufficient for many physical problems.