We present an in depth analysis and a new derivation of the Doppler factor in the Linard–Wiechert (LW) potentials, based on geometrical considerations in Minkowski space. We argue that, contrary to a common assumption, the methods used for deriving the Doppler factor in the case of an electrically charged extended particle are not applicable in the case of a point particle. A geometrical interpretation of the Doppler factor is nonetheless found in the later case, based on the electromagnetic interaction model of Fokker. In this model the interaction takes place between infinitesimal worldline segments with end points connected by light signals, just like the points where light pulses are emitted and detected in general. This analogy reveals that the relativistic Doppler effect is the missing link between the classical Doppler effect and the Doppler factor in the LW potentials.

我们基于 Minkowski 空间中的几何考虑，对 Linard-Wiechert (LW) 势中的多普勒因子进行了深入分析和新推导。我们认为，与常见假设相反，在带电扩展粒子的情况下用于推导多普勒因子的方法不适用于点粒子的情况。尽管如此，多普勒因子的几何解释仍可在后一种情况下找到，基于 Fokker 的电磁相互作用模型。在这个模型中，相互作用发生在无穷小的世界线段之间，端点由光信号连接，就像通常发射和检测光脉冲的点一样。