A perfect mirror covered the inside surface of a sphere (assumption: there is no any loss during reflection and reflections continue endless) and there is a very small laser on point $A$ in the surface of the sphere and the direction of the laser light goes to inside and reflects from other point $B$ in the surface of the sphere.
What are the whole possible mathematical conditions to get periodical reflections. (Passing again from $A$ to $B$)
Thanks a lot for answers