Dispersion relation describes the relationship between wave number and angular frequency, denoted as k(ω). For a free electron, it relates momentum (p) to energy (E), represented by the equation p = √(E² - m²). This relationship can be integrated into the electron wave function, influencing the group velocity, calculated as dE/dp = p/E. The discussion emphasizes the significance of this relation in understanding wave behavior in quantum mechanics. Overall, the dispersion relation is crucial for analyzing free electron dynamics.