What kind of mirror does the "this kind of mirror" mentioned in the picture refer to?

This kind of mirror: refers to a "two-way glass mirror". It is a mirror in which you cannot see others but others can see you. This kind of mirror exists in reality.

Attention: When girls go to public places such as public bathrooms and locker rooms, please pay attention to whether the glass surrounding you is a real mirror or two-way glass.

Identification: Is the "finger method" really effective in identifying this kind of glass? Mirrors can see people by reflecting light. However, it is not the glass itself that reflects the light, but a thin reflective layer (usually a metal such as silver or aluminum). For common mirrors, the reflective layer is coated on the back surface, and the light will be reflected back when it hits the back surface of the glass.

Every object that the light hits before being reflected back will appear in the image in the mirror. If you press your fingertips on the mirror (the front surface of the glass), your eyes will see the "behind the mirror" first. A glass of the same thickness, and then the image of the finger, there will be a distance between the finger and the mirrored finger, so they will not stick together.

As shown in the picture above: stick your finger to the front surface reflector, the real finger and the fake finger will stick together. Obviously, this finger detection method is suitable for distinguishing between normal mirrors and mirrors with front surface reflections.

But generally in public places such as bathrooms, you will not see the kind of mirrors that only appear in precision instruments. In these places, if you find that your fingers and mirrors are stuck together, you may have encountered two-way glass with a semi-reflective film on the front surface of the glass. Be careful to protect your privacy.