# On the optical equivalent of the Michelson interferometer

How can it be? Where did the beam splitter go? And in the second system we restrict the incident beam of light from the source to be making the same angle $$\theta$$ with respect to the normal of both mirrors, this was certainly not the case in the Michelson interferometer (the beam of light striking mirror 1 could for example be at $$\alpha$$, while the one striking mirror 2 could be at $$\beta$$), so why add this restriction?
• I respectfully disagree, the point source is in front of the screen in the second diagram, whereas it is at a $45°$ with respect to screen in the second. I've been contemplating the second figure for a while and still can't see why restricting the ray that strikes mirror M1 and the one that strikes mirror M2 to the same angle is a legitimate move from the first to the second diagram. Shouldn't we have something more general, like this, for instance. Feb 7, 2020 at 19:41