A focal arrangement that has a secondary mirror that reflects the focused light back through a hole in the primary mirror is a _______________.
a. Cassegrain focus
b. Newtonian focus
c. Schmidt-Cassegrain focus
d. Schmidt focus
a. Cassegrain focus is the focal arrangement in a Cassegrain reflector used in optical telescopes and radio antennas. The primary mirror is a concave mirror, and the secondary mirror that reflects the focused light back to it is a convex mirror.
