Why can light pass through glass?

In modern life, glass has become an indispensable material, present everywhere from houses, shops to office buildings.

Whether it's sunny or rainy, the transparent glass windows still allow us to enjoy the outside view without worrying about the weather.

However, few people really understand the mechanism of operation and why light can easily penetrate this familiar material.

Glass windows first appeared in England in the 17th century. Since then, the glass industry has continued to develop, bringing the durable and perfectly transparent products we have today.

Research on glass continues, moving toward more advanced applications, such as self-cleaning materials or even glass that can heal itself after breaking.

Why can light pass through glass?

The transparency of glass is closely related to its amorphous structure. Glass is made by melting sand (containing quartz crystals) at high temperatures (over 1,600 degrees Celsius), then cooling it rapidly.

This process causes the atoms and molecules to not have time to arrange in a certain order, forming an amorphous solid - an intermediate state between solid and liquid.

Professor Philp Moriarty from the University of Nottingham, UK, explains: "In materials like glass, electrons need a lot of energy to jump between energy levels, and visible light photons are not strong enough to trigger that jump.

Instead of being absorbed or reflected, light simply passes through. That's why we can see through glass, because it is transparent to visible light."

He also compared it to paper: "The reason you can't see through a sheet of paper but can easily see through a thick sheet of glass is because glass is amorphous, so it doesn't have order, but it also doesn't have many defects.

On the wavelength scale of light, glass is uniform. Paper is made up of many fibers, and these fibers – their size, diameter, width, spacing – do not vary much with the wavelength of light, and so they scatter the light. The result is a sheet of paper that is opaque, not allowing light to pass through."

Manufacturing process affects light transmission

To create clear glass, quartz sand is heated to its melting point, causing the crystal structure of the quartz to break down.

When cooled rapidly, the material turns into an amorphous solid. The rapid cooling process also helps shape and harden the material, turning it into familiar window glass.

To optimize the production process, scientists found a way to lower the melting temperature of sand by adding sodium carbonate.

However, this reduces the chemical resistance of the glass. To overcome this, calcium carbonate is added as a stabilizer, which improves the impact resistance of the glass.

Thanks to constant improvements in manufacturing processes, we can now enjoy natural light through glass windows while being protected from the elements and the outside environment.

Research on glass continues to open up many more potential applications in the future.

Source: https://dantri.com.vn/khoa-hoc/vi-sao-anh-sang-co-the-xuyen-qua-kinh-20250818011425290.htm