An electromagnetic wave is transformed in a remarkable way by a transient magnetoplasma medium. The main effect of the temporal change in the parameters of the medium is the splitting of the source wave into new waves whose frequencies are different from the incident wave frequency. Several transient problems  involving slow or fast creation or slow or fast collapse of the plasma medium in the presence of a static magnetic field will be discussed. Approximate perturbation solution for the case of rapid temporal change of the plasma medium, based on time-domain Green's function, will be presented. WKP or Adiabatic analysis for the problem of slow temporal change of the plasma medium will also be presented. Finite Difference Time Domain (FDTD) method of numerical solution will be developed. Several interesting results obtained by the author by using the approximate solutions and verified by the FDTD method will be discussed. The more important results are: (1) frequency upshifting with power intensification of a whistler wave by a collapsing plasma medium, (2) conversion of a whistler wave into a controllable helical wiggler magnetic field, (3) mode coupling due to a magnetized plasma in a cavity, and (4) frequency down-shifting due to switched plasma layers in the presence of a background magnetic field. A switched magentoplasma can act like a frequency transformer. The source wave can be generated in an available frequency band and the switched plasma device converts the source wave into a new wave in a frequency band not easily obtainable by other methods. Frequency shifting mechanism can be applied for plasma cloaking of satellites and aircraft and for producing short-chirped-pulses as ultra wide band signals. Recent proof of the principle experiments confirmed many theoretical results. Many more experiments need to be done to study the scalability of the results. Fast Switching of magnetized plasma is a challenging experimental task.