Consider two waves y, = a cos(ot - kz) and y, a cos[(o + ao)t - (k + ak)z]. the group velocity of the superposed wave will be (ao << o and ak << k (-a0) (a) (b)

Consider two waves y, = a cos(ot - kz) and y, a cos[(o + Ao)t - (k + Ak)z]. The group velocity of the superposed wave will be (Ao << o and Ak << k (-A0) (A) (B) (20+) k-Ak) (2k Ak) (C) (D) (+A Ao) (k Ak)