How It Works
Stained glass window in Siena

How is glass able to block infrared light?

Stained glass window in Siena

Infrared light is a form of electromagnetic wave consisting of longer wavelengths than that of visible light.

How any light interacts with materials depends on the arrangement of atoms – specifically the arrangement of the electrons – in the material, and the wavelength of the incoming light.

Various wavelengths of light have different amounts of energy, and electrons in all materials are selective about which energy will make them absorb light or allow it to pass through.

Visible light will not be absorbed by the electrons in glass, so it shines through. Certain wavelengths of infrared light can also pass through glass, but many are blocked as their energy is absorbed.

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