ABSTRACT
In the late 1970s Garetz and Arnold demonstrated that when a circularly polarised ( ¼ 1) wave was transmitted through a half-wave plate rotating at =2, its frequency was shifted by (6.1). Garetz recognised that the frequency shift was an example of a more general angular Doppler shift (6.2, Paper 6.1), which was manifest whenever light was emitted, absorbed or scattered by rotating bodies. The frequency shift can be understood in terms of energy conservation or, more sophisticatedly, by a Jones matrix analysis. Subsequently, the same type of experiment was described in terms of a dynamically evolving Berry phase (6.3). The shift is analogous to the speeding up or slowing down of a clock hand when the clock is placed on a rotating turntable.
