Physics, Relativity, Muon, Quantum Physics, Particle Physics.
Application of Relativity in its entirety, in fact, dispenses altogether with working out of the classical Doppler Effect. Further, the Lorentz transformation of a single electromagnetic wavelength and its time period in either of the frames lead to the same result, which is shown below. Let 𝜆𝑠, 𝑡𝑠