hi.
"An approach to the problem of optimum directive antennae design,"
AI Uzkov, “An approach to the problem
of optimum directive antennae design,” Comptes Rendus (Doklady) de l'Aca ...
Qote
Figure 5. The reflector is assumed to be perfectly conducting, so that the rays are completely reflected.
http://www.antenna-theory.com/antennas/reflectors/dish.php