Can infrared rays be cracked with red wine?

In some movies, infrared sensors are not used as mirrors or sensing devices, but as "safety devices". Install a laser anti-theft device in the room where the important vault is placed. Once there is an intruder, the alarm will sound. Although the eyes can't see it, the laser is densely distributed around the room like a spider's web. As long as it touches the laser line, the alarm will sound. After installing an oscillator and a receiver at the tail of one end and the other end, if the receiver can't receive the laser emitted by the oscillator for a moment, it will think that something has entered between them and the alarm will sound immediately. The laser used at this time is infrared.

This safety device is also installed in the exhibition hall where precious works of art are stored in the film Crossing the World. But professional thieves Chow Yun Fat, Leslie Cheung and Cherie Chung passed the security check beautifully. The way for them to escape from the room is to pour the prepared wine into the cup and observe the room through the cup before entering the room with safety devices. So you can see the laser? They danced excitedly and fled freely. The art gallery that only believed in safety devices was finally robbed.

But although it looks so perfect, in fact, this kind of thing is absolutely impossible. Because it is impossible to see the laser even through a glass full of wine. What about smoking? Can't you see clearly that infrared rays pass through the smoke with smoke?

Unfortunately, this may not work either. In fact, we can see the light passing through the smoke. This phenomenon is called "Tyndall phenomenon" in physics. Because light will scatter in all directions when it meets smoke particles, what we see is the phenomenon of light beam. However, the infrared wavelength is long, and almost no scattering occurs. Because the degree of light divergence is inversely proportional to the wavelength. More precisely, the divergence angle of light increases inversely with the fourth power of wavelength. Blue light or ultraviolet light with shorter wavelength has larger divergence, while red light or infrared light with longer wavelength has weaker divergence. This is why the sky looks blue. The blue light with the strongest divergence from the sun enters our eyes, and the sky looks blue. Similarly, infrared light is not obvious in smoke, so it is actually difficult to see. One of the reasons for using infrared ray in safety equipment is that it can be easily manufactured with less energy. However, there is no sparking phenomenon, so don't worry about the benefits of being discovered.

Then there is one last question. If you use an infrared camera, can't you see the infrared laser of the security instrument? Although it is a good idea, the people who study safety equipment are not ordinary people.

The laser emitted by the safety system is not a continuous signal, but an intermittent signal. Because the short message number is transmitted instantaneously, even the infrared camera can't see it. In addition, the signal is sometimes strong and sometimes weak, which is difficult to capture with a camera. Finally, it is concluded that it is very difficult to break through the infrared laser sensor. Science and technology have expanded human vision to the infrared field, providing us with a new perspective to see the world. The world seen by infrared rays, just like the earth seen by predators, is not beautiful and fuzzy, but it is definitely a world that can feel vitality. In the future, science and technology will continue to speed up and develop mechanical devices to overcome the boundaries of our vision.