text: The imaginary part of the propagation constant is this quantity's namesake constant.
full_question: The imaginary part of the propagation constant is this quantity's namesake constant. This quantity isplotted against frequency on the second, or lower, Bode plot. A form of this quantity symbolized gamma maybe nonzero after a cyclic adiabatic process, or if an electron passes near a solenoid even where no magneticfield is present. The wavelength over the period is its namesake velocity, which contrasts with the groupvelocity. For AC quantities such as current and voltage, this quantity is symbolized by a vector rotating arounda circular plot. A difference in it for two equal-frequency waves can lead to destructive interference. For 10points, name this quantity symbolized phi in the wave equation, the geometrical shift to where a wave begins. 
first_sentence: The imaginary part of the propagation constant is this quantity's namesake constant.
raw_answer: phase [or phase constant; or phase velocity; or phase ratio; or Berry phase; or phase shift] 