# Velocity of Wave Packets

by Hyperreality
Tags: packets, velocity, wave
 P: 203 Wave packets has a group velocity of $$v_{group}=\frac{d\omega}{dk}$$ and its phase velocity is $$v_{phase}=\frac{\omega}{k}$$ Show that the group velocity and the phase velocity are related by: $$v_{group} = v_{phase} - \lambda\frac{dv_{phase}}{d\lambda}$$ Can someone please tell me where to start on this problem?
 Sci Advisor HW Helper P: 11,948 All u need to know besides the rules of differentiation is $$k=:\frac{2\pi}{\lambda}$$ Daniel. PS.Compute the RHS of your equality and show it matches the LHS.