Reflects glass light
Glass has an amorphous molecular structure without boundary layers and behaves optically isotropic as long as there are no internal stresses or external loads. However, glass is only permeable to part of the entire light spectrum. Part of the light is retained by absorption in the glass, another part is reflected back at the interface. The following applies to the degree of transmission t, the degree of absorption a and the degree of reflection r:
t + a + r = 1
In the case of commercially available flat glass, the degree of transmission is 83% - 90%, depending on the glass thickness; with normal incidence of light, about 8% of the light is reflected at the boundary surfaces. Commercially available glasses have a refractive index of approx. 1.5. The cause of the refraction is the change in speed of the light in the interface. The frequency of the light remains constant, only the wavelength changes.
The reflectivity can be specifically influenced by anti-reflective coatings with a defined refractive index or by fine etching of the surface. Due to the scattering of the light, the specular reflection then changes into a diffuse one. The absorption capacity of the glass is strongly dependent on its composition. Glasses in the visible spectral range are normally completely colorless. If the glass contains small amounts of components from subgroup elements (Cu, Ti, V, Cr, Mn, Fe, Co or Ni), electron jumps occur even with light with a relatively low energy, in which energy is absorbed. The glass thus shows discoloration in the visible area, which depends on the type of element. By using special admixtures, this effect can be used to color the glass in a targeted manner.
The commercially available flat glass is therefore almost impermeable to light in the ultraviolet range (UV). There is a pronounced absorption edge in the range of wavelengths λ = 150-250 nm. The position of this absorption edge shifts into the longer-wave range depending on the composition and alkali content. In the infrared range (IR), normal glass shows more or less pronounced absorption bands that are caused by an interaction of the light and components of the glass. All silicate glasses are impermeable to infrared rays with a wavelength above λ = 5,000 nm.
The absorption capacity in certain spectral ranges can be influenced in a targeted manner by means of special compositions of the glass or coatings. An example of this are sun protection glasses with the lowest possible transmission values in the harmful infrared and ultraviolet spectral range.
Expertise on the subject
Manufacturing / properties
Chemical composition and resistance
Silicate glass is used almost exclusively in construction. Mostly the soda-lime-silicate glass, which was already used by the Egyptians ...
Manufacturing / properties
The light permeability of glass is specified in DIN EN 410 Glass in Building - Determination of the photometric and ...
Sun protection: sun protection glasses
Just as with thermal insulation glazing, ultra-thin low-E coatings made of precious metals are used today for solar control insulating glass ...
Sun protection: UV transmission
Ultraviolet (UV) radiation is part of the electromagnetic spectrum, beyond the violet radiation that is still visible. You...
BauNetz Wissen Glas sponsored by:
Saint-Gobain Glass Germany
- Which schnapps has no yeast?
- Why are pearls still common in Japan?
- Will robots replace cooks in the future
- Is it legal to leave a home?
- Why do metals become more difficult to weld?
- What is real true religion
- How do you say sister in Cebuano
- Can the United States ever be conquered?
- The Kardashians have been canceled
- How does the reservation end
- What is water phantom in radiation therapy
- Is it true that Blackpink is not talented
- What problems could the social problems be?
- Why am I so self-destructive
- Is steampunk science fiction or fantasy
- How do zoos affect agriculture?
- How are different fonts named
- What important events happened in 2002
- What does the DAlemberts principle say
- Well worth the IMAX experience
- Can I wear a used emerald gemstone
- Why should people calm people down
- Who owns the internet
- What was George Bush like as governor
- Who are the customers of online taxi
- Can I buy a property in Dubai
- 3D TV is dead
- Who works every day
- Will my PCOS ever go away
- Was Bob Ross different in the military
- How cold is the winter in Dubai
- Why is Aqua Regia called royal water
- Is Donald Trump a misanthropist
- Can I be a bisexual hetero romantic?