We call this a one-way mirror. https://en.m.wikipedia.org/wiki/One-way_mirror https://en.m.wikipedia.org/wiki/One-way_mirror They are not perfect (intensity &

We call this a one-way mirror. https://en.m.wikipedia.org/wiki/One-way_mirror https://en.m.wikipedia.org/wiki/One-way_mirror They are not perfect (intensity & wavelength limitations), but they exist. See also mirages and total internal reflection.