= Solution
Relativistic <relativistic aberration> concentrates emission into an angular scale
$$
\boxed{\Delta\theta\sim\gamma^{-1}=1.70\times10^{-4}\ \mathrm{rad}
=0.170\ \mathrm{mrad}.}
$$
This is a half-angle or characteristic divergence scale; a full cone opening is about twice it. The exact half-photon-count cone in <1/a> applies to isotropic rest-frame emission. A synchrotron emitter has its own rest-frame angular radiation pattern, so that count result should not be treated as an exact median-power formula for the synchrotron beam. It nevertheless gives the correct <relativistic beaming> scale. Electron-beam emittance, vertical angular spread and the detector's acceptance can broaden the experimentally observed divergence beyond this intrinsic estimate.
Back to article page
