3. Assume that we have a lossless waveguide of width a, height b surrounding a dielectric medium with€, Ho. We want to discuss an input signal with frequency w, sufficiently large for a TE11 operating mode. (a) Find the group velocity of the resulting wave. (b) Find the phase velocity of the resulting wave.( (c) What conditions for a, b would allow the group and phase velocities to converge? What physical meaning does this limit have? Hint: focus on the waveguide's influence on the medium.