Moving-mirror photon interception rate
= Moving-mirror photon interception rate
{title2=$R_{\rm hit}=R(1-\beta)$}
For a <photon> emitted from the origin and arriving at receding mirror position $x(t)$, its emission time is $t_e=t-x(t)/c$. Thus $dt_e/dt=1-\beta$ and a steady source rate $R$ gives impact rate $R(1-\beta)$ in source-frame coordinate time. This is distinct from the emission rate and from a rate per mirror <proper time>.