This is not a homework question. It may appear as noob to most of you but SR is not my area of expertise and hence it seems very complex to me.
Question: Consider that there are two in-line pin hole separated by some distance. Both the pinholes at rest w.r.t to each other. There is a light source that moves relative to the pinholes. The relative movement is normal to line joining the pinholes.
Case 1: I consider that pinholes is the rest frame and light source as moving. In this configuration when the light source and one of the pinholes are overlapping, a pulse of light can pass through the first pinhole and strike the other pinhole, passing it too.
Case 2: Now I consider pinholes to be moving and light source to be rest frame. From the rest frame of light source, I see that a pulse of light passes through the first pinhole during the overlap. This light pulse will travel to other pinhole but will not be able to pass the second pinhole because the pinhole has already moved. (For this to happen, I will assume suitable relative velocity and separation between the pinholes so that the second pinhole has moved enough to avoid avoid the light ray)
So, you see that although these two are equivalent scenarios, their result is not same. Now I believe that I might be wrong because the relative motion and light are normal to each other and hence it does not qualify to be equivalent scenarios and so their results are not bound to be same. Is my thinking correct? Or is there any other explanation or am I missing something important here?