Do you know how other people see you? Of course, we are all familiar with our reflection in the mirror, but it does not correspond to the sight that our counterpart has in front of their eyes. The AstroMedia right-angle prism is one of the so-called deflecting prisms and allows us to see from the point of view of our counterpart.
The right-angled prism owes its power of deflection to its property of total reflection: if a light beam enters the prism perpendicularly and hits the 45 ° inclined surface, it cannot leave the prism at this point but is reflected inside it, until it can exit again.
This is due to the large difference in the refractive power of air and crystal glass. If the two had the same refractive index, the light would not be deflected but could leave the prism again in a straight line. If there is only a simple reflection, an image is mirrored. In the case of a double reflection, the reflection is canceled by a new reflection, the reflected image appears the right way round.
In this way you can see your own face reflected in the prism, it appears as other people see us, and not as the familiar reflection from our everyday life.