Is there any secret in the hotel mirror?

How to judge whether the bathroom mirror is single-sided or double-sided when staying in the hotel to prevent being peeped; How to clean the troublesome hair when sweeping the floor; How to peel grapes easily and gracefully? Are these tips useful or not? In this issue, to be honest, the reporter personally tested it. Disclaimer: If there is no "greasy" mirror behind the bathroom mirror, you know that you can go to the bathroom in hotels, hotels, gyms and other places and point your fingernails at the mirror. If there is a distance between the image in the mirror and the nail, then the mirror is a one-sided mirror; If there is no distance between the image and the nail, it means that it is a double mirror, which means that you are likely to be exposed to others' sight. Truth: What are the useful double mirrors in some situations? I believe everyone has seen it when watching American TV series: in European and American movies or TV series, the suspect will be taken to a room with a mirror by the police for interrogation. On the other side of the mirror, a police officer can observe the suspect in the room through the mirror. This is a double mirror. Double mirrors are also called two-way mirrors and one-sided perspective glass. Its principle is to coat a thin film of chromium, aluminum or iridium on ordinary glass by vacuum coating. This glass can reflect most of the projected light back. It is an ideal choice for surveillance, security and monitoring, but it is often used for voyeurism. In a well-lit room, one side of a single-sided mirror looks like a mirror, but from the other side, it is an ordinary stained glass window. If you walk into the bathroom of a hotel while traveling, all you see is a mirror, but people outside can see inside. Isn't that terrible? No privacy at all. The tips mentioned above are all tested by the author himself and are effective in some cases. But physicists warn that this method is not suitable for all bidirectional mirrors, because as long as a layer of glass is added in front of the bidirectional mirror, or the coating is a "sandwich" in the middle of the glass, this method will not work. Nowadays, many bidirectional mirrors will be installed in this way, because they are afraid that the special film layer will be too thin and accidentally scratched. But if you look closely, you can see that the edge of the glass is layered. In addition, according to the "user's guide" of the two-way mirror, it is only when the observed person is in a very bright environment and the person behind the mirror is in darkness that it is possible to achieve the effect of "peeping". Therefore, compared with the "finger method", the netizens of Guoshuwang gave a more effective judgment method: turn off all the lights and aim the flashlight at the mirror. Or stick your eyes on the mirror, block the light with your hands, and take a closer look at whether there is anything behind the glass.