How does light penetrate solids, and can light pass through solid metals?

The concept of light in optics can also be extended to the infrared and ultraviolet fields, and even X-rays are considered light, while the spectrum of visible light is only a part of the electromagnetic spectrum. Light has wave-particle duality, that is, light can be regarded as a very high frequency electromagnetic wave, and light can also be regarded as a particle, that is, light quanta, referred to as photons.

If the iron sheet is made to be quite thin, it is also transparent. Some sunglasses actually have a thin layer of metal plated on the glass lens, but this metal film is quite thin and also transparent.

The so-called absolutely transparent and absolutely opaque objects do not exist, and the transparency and opacity of solids are relative. It's just that some materials are a little more transparent, and some are a little less transparent. This is because different solid substances have different blocking abilities for light.

Imagine that if the glass is made thick enough to block light enough, the glass will also be opaque. It's like the sun can't reach the bottom of the ocean.

Some solid opacity is also related to its internal structure, such as a piece of paper in drying, the transparency is poor, but after wetting or soaking in oil, the transparency is greatly improved, because water and oil fill the internal holes of the paper, thus reducing the loss of light caused by the diffuse reflection of light in the paper.

Light is both fluctuating and particle-like.

Penetrating solids is explained in terms of particle-like properties, treating light as photons with energy (like bullets).

The nuclei that make up atoms are extremely small, the electrons are even smaller, and most of the volume inside the atom is empty.

Photons can pass through atomic space, but when they touch the nucleus, they will come back, which is a reflection phenomenon.

Different substances have different photon penetration capabilities.

If there is a certain angle, it is refracted in and refracted out; If it is shot perpendicular to the projectile (smooth), it does not refract and passes through directly.

It goes in by refraction, it comes out by refraction, and it travels in a straight line in the solid.

Solid light transmission is nothing more than invisible light with a high frequency.

According to foreign ** reports, when researchers recently irradiated a special light on a piece of metal with many irregular holes, they found that all the light shining on it became like a liquid into the metal sheet, and then found a path to shine out from the other side.

It's pretty incredible. Imagine shining a beam of light on a colander used in your kitchen, and some of that light will pass through the holes in the colander, but a large part of it will always be blocked by the solid part of the colander. In contrast, terahertz rays (a type of low-frequency light in the region between microwaves and infrared rays, sometimes called T-rays) can pass through a sheet of metal through irregular holes when they hit it.

Ajay Nahata, a physicist at the University of Utah who conducted the experiment, said: "You can let this light pass 100 percent through the sheet of metal, even if the hole on it only takes up 20 percent of the area. ”

As simple as it sounds, it is still a relatively new theory to understand how so much light passes through these holes. The first to explain this was Thomas Ebson, who published a study in 1998 that said that the amount of visible light passing through a single hole was more than scientists had originally expected. Since Ebson's discovery, researchers have speculated that this theory can only be applied to visible light passing through small, regular-shaped holes, such as squares.

But in their latest experiment, Nahata and his colleagues found that light can pass through the surface of a sheet of metal and then drill through the irregular holes in the sheet and out of the other side of the sheet.

Nahata and his colleagues were also the first researchers to discover the reaction between terahertz rays and metals and the small holes on them, because visible light oscillates too fast and is therefore difficult to measure, while scientists were able to accurately measure the frequency of low-frequency terahertz rays. By using terahert rays, it is possible to clearly see how and when the light comes out of the small holes of the metal sheet. When you shine light on these little holes, some of the light passes through directly, while some of it comes out after a while.

Because all light waves tend to behave similarly, the researchers speculate that the activity of the terahertz rays they observed is also present in other electromagnetic waves.

Researchers at the University of Utah hope to apply terahertz rays to wireless communications and homeland security activities.