Sayed,  As a nature of electron optics, reflection angle is always larger than incidet angle.  In case of flat mirror, the reflected ellectron collimated beam becomes diversive.   In case of concave mirror, the reflected electron collimated beam focuses  with negative spherical aberration. In this analogy, chromatic aberration, which is generated by the initial velocity distribution of electrons, is always negative.  Shigeo

This is a trivial to show, this is one of test examples of EOD.