The instantaneous expression for the electric field in a uniform plane electromagnetic wave (UPEMW) propagating in vacuum is given to be E(z, t) = ix Ez(z, t) where Ez(z, t) = 5 cos[21.109t + (20n/3)z -60°), mV/m. [4] If the wave in problem [3] now instead propagates in a lossless dielectric medium, what will be the instantaneous expression for the wave electric field if you are given that the relative refractive index ny of the medium of propagation is 3. You may assume the same amplitude of 5 for the electric field and the same frequency and polarization of the wave as in problem k. Also assume the same phase factor of 600 in the expression of the electric field. NOTE: As you may recall from your study of physics, the term relative refractive index ny of the propagation medium is defined by the ratio n = c/ph>=1, i. e., ny represents a velocity reduction factor relative to the velocity of the EM wave in vacuum. Thus, the velocity of EM wave in a dielectric medium is simply equal to the velocity of EM wave in vacuum c = 3.108 m/s divided by ny. It should be apparent that an EM wave propagating in a dielectric (or insulating) medium has a shorter wavelength than an EM wave of the same frequency propagating in vacuum as dictated by the relationship 2.4 = Vrh,