A couple checked into the hotel and accidentally discovered that the window on the wall was a "single-sided window". From the room, they looked like a mirror, but outside the window, they could see the situation inside the room. The incident caused a sensation after it was exposed. Everyone condemned the hotel for being "unscrupulous". At the same time, they were curious how this "single-sided window" was transparent like a mirror and the other side. Is this a new high-tech?
schematic picture, has nothing to do with news events
In fact, any piece of glass window can be regarded as a "single-sided window" or "two-way visual mirror". It mainly depends on how you use it. From a scientific point of view, this is not a high-tech.
Mirror is a common object in our lives. Everyone knows that one side of the mirror can clearly reflect portraits or scenery, while it is opaque from the other side. It uses the principle of reflection of light.
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Since the new Stone Age , our ancestors have made mirrors with bronze. Bronze mirror is mostly round, with exquisite patterns on the back, and the front is polished and polished to clearly reflect the figure.
polished metals can be polished when the mirror
glass appears, people start to cover the flat glass plate with metals such as tin, lead, gold, silver, etc. The metal reflectivity is high, and the hard glass can protect the metal reflective surface from scratching, so that the mirror can be used for longer.
With the advancement of technology, the mirror production process has also been further developed. Most modern factories use the method of vacuum coating to allow metal atoms such as silver to evenly cover the glass surface, which can not only grasp the reflectivity of the glass, but also save the use of precious metals to reduce costs.
visible light cannot pass through metal. When photon irradiates on the metal surface, it will be rebounded by the metal surface " free electron ocean", so there is no so-called "transparent metal". Vacuum electroplating technology is to evaporate metal atoms and allow them to evenly adsorb on the glass surface. The metal film formed is only one or two atoms thick and discontinuous. There are spaces to drill. Some light waves can pass through the gaps between metal atoms, and the other part is reflected. By adjusting the thickness of the coating, we can control the transmittance of the glass .
coated glass is widely used in building doors and windows
Modern building exterior walls use a large number of coated glass, which is conducive to lighting on the one hand, and can block ultraviolet rays and infrared rays , thereby achieving energy-saving effects.
Any coated glass transmits light in bidirectional direction. If the light energy illuminates from A to B, it can also illuminate from B to A. The transmittances on both sides are basically the same, otherwise it will violate the thermodynamic law .
Since both sides can be seen, why are there "single-sided visual glass" or "single-sided window"?
Some friends have experienced the embarrassment of hitting glass - when we walk out of the dark-light house, we often "turn a blind eye" to the glass door in front of us, and then bump into it - that is "what a painful understanding" and what an embarrassing life experience!
How painful is
The flat glass surface will reflect light. The glass coated with a metal film can reflect more light, and at the same time, it also allows part of the light to penetrate. The penetration rate of light in both directions is equal.
But when there is a significant difference in the intensity of light on both sides of the light glass, the light reflected on the bright side (side A) is stronger, and we can clearly see our reflection - the glass looks like an ordinary mirror. At the same time, part of the light passes through the glass to the darker side (side B). The observer on the B side can also clearly see the A side, and he will even ignore the existence of the glass. At the same time, because the light on the B side is weak, its light intensity is far less than that on the A side, so when the light transmits through the glass from the B side, it will be submerged by the strong light on the A side.
"Single-side visualization" is related to the light intensity
On the other hand, if the light on the A side is very dark and the light on the B side is turned on, we look at the glass from the B side like a mirror, while looking at the B side is completely visible.
This is why some friends bought glass film and pasted it on the window, but found that it could not block privacy at night: after turning on the light at night, the light inside the room is stronger, the outside of the room is darker, and more light passes through the glass to the outside, but you have no idea about it.
Glass film can reflect sunlight but cannot protect privacy
What is there to tell if a mirror is "single-sided visual glass"?
Some people say that poke the surface of the mirror with your fingernails. A normal mirror can see a gap between the nail and the reflective surface. There is no gap between the "bidirectional visual mirror" or the reflection image is dim.
Nail poke mirror is an error demonstration
Is this true?
It's a pity that this is a demonstration of error.
Finger nail poking mirror can only determine which side of the metal reflective layer is. In order to eliminate the artifacts caused by glass refraction, some high-end mirrors have a reflective layer on the outer surface rather than the inner surface. Therefore, it is wrong to judge the "double-sided mirror" by relying on "artifacts".
A more scientific way is to use light: turn off the light first to keep you in a relatively dark environment, then turn on the flashlight, or the fill light on your phone, and illuminate it against the surface of the mirror.
Use a flashlight to look in the mirror to observe more scientifically
All "double-sided mirrors" are coated glass, which can reflect a certain proportion of visible light and allow part of the light to penetrate the metal film to reach the other side of the glass. In this way, we can observe the opposite image by illuminating the glass with strong light.
Of course, you can also carry a small makeup mirror with you, paste it on the surface of the test mirror, and judge whether it is "two-way visual glass" by judging the clarity of the two images. This method is not as simple as a flashlight and is prone to misjudgment, so it is recommended that you turn on your phone and try it.
If you are not at ease with the window glass, the safest way is to pull up the curtains.
