No, it’s not a one way mirror. It’s much cooler than that. MIT scientists have invented a new invisible mirror that can show reflections like a typical mirror but also be see through like a window. The magic is in the alternating 84 ultra thin layers typical glass and tantalum oxide. It’s a mirror but when you spin it, it becomes transparent. Some light passes through, some light gets reflected.
As light passes from one of these layers to the next, some gets partially reflected — except for light that approaches from a certain angle. Any light that hits the surface of a layer at this so-called Brewster angle, and with a particular polarisation, will pass straight through as if the surface wasn’t there. The Brewster angle is different for each pair of materials as it depends on their refractive indices.
Check it out in action below: