Why glass transparent

Exactly the same happens with X-rays for which our body is nearly transparent whilst a metal plate absorbs it. This is experimental evidence.

Any photon has certain frequency - which for visible light is related to the colour of light, whilst for lower or upper frequencies in the electromagnetic spectrum it is simply a measure of the energy transported by photon.

A material's absorption spectrum which frequencies are absorbed and how much so depends on the structure of the material at atomic scale. Absorption may be from atoms which absorb photons remember - electrons go to upper energetic states by absorbing photons , from molecules, or from lattices. There are important differences in these absorption possibilities:. As glass is a non-crystalline, overcooled fluid, consisting of molecules, its absorption occurs in the 1st and 2nd ways, but because of the matter it is composed of, it absorbs outside our visible spectrum.

Essentially because of absorption. When photon flies into the material it interacts with its constituents. This interaction can be divided into two contributions. One of them is elastic and is the source of the index of refraction because effectively it just slows the photon down while the other one is inelastic.

Photon gets absorbed by an atom say and later it is emitted as thermal radiation in random direction thereby losing the original information it carried. When you look at this macroscopically, this process will be described by some parameter like penetration depth and intensity w. So if you made opaque objects thin enough, they would still be transparent although the outgoing light would be weaker depending on thickness.

Of course, this discussion completely avoids surface effects reflection, refraction, scattering, etc. Note that all of this depends on frequency of the incident light. Atoms let's just talk about them for simplicity; in reality there will be contribution also from molecules, lattice, free electrons and whatnot have something called absorption spectrum.

This arises because for certain frequencies electron can catch the photon and get excited to the higher energy state. So, while a material can be transparent in certain range of frequencies like glass is for visible light it can be quite opaque in others.

This may be a little technical, but I always thought it was cool: one of my professors once pointed out that transparency only happens because the material is approximately a linear dialectic over the frequency range that you care about.

Turns out water is a linear dielectric over precisely the range of frequencies our eyes can detect. There is a lot of nonsense around about this. It is NOT a very thick stiff or cold liquid, nor is it due to how ordered the structure is. In simple terms it is all about the electrons in the substance. When photon of light enters a substance, it will interact with an electron changing its energy state.

In common opaque material, it takes a small amount of energy to move the electron from its resting energy state to a higher energy state, so the low energy photon of visible light is absorbed, transferring its energy to the electron which in turn moves to a slightly higher energy state. In much rarer transparent material the distance between the electrons rest energy level and the next higher state is much much greater.

Although the individual atoms in the glass would scatter the light in different directions, just as a stick in water will scatter a water wave. However if you put a lot of regularly placed sticks in water, much closer than the wavelength of the water wave, the scattered waves from the different sticks will not be in phase except in the forward and backward directions.

That means that when you add the waves in other directions the crests and troughs will cancel. Something very similar happens for light hitting glass. Some of the light bounces back from the surfaces and some transmits through.

It doesn't scatter off to the sides, except for a small amount due to small unevenness in the density of the glass. That glass window is doing what it does best — keeping the inclement weather out while still permitting light to pass through.

The substance absorbs the photon. This occurs when the photon gives up its energy to an electron located in the material. Armed with this extra energy, the electron is able to move to a higher energy level, while the photon disappears.

The substance reflects the photon. To do this, the photon gives up its energy to the material, but a photon of identical energy is emitted. The substance allows the photon to pass through unchanged. Known as transmission, this happens because the photon doesn't interact with any electron and continues its journey until it interacts with another object. Transparent Glass FAQ Why is glass transparent to visible light but opaque to ultraviolet and infrared?

This is because of the energy UV and infrared light hold and their wavelengths. When visible light transmits through glass, waves don't have enough energy to excite the electrons within, so they pass right through the crystallized structure, thus causing transparency.

Why is glass transparent while any typical metal is opaque? This concept is also known as diaphaneity or pellucidity. While light waves don't have energy to excite and reflect off of glass' electrons, the same cannot be said about other metals. Light touches electrons, excites them and bounces back, which allows us to see the metal. Is glass always see-through? Not all glass is transparent — sometimes it is translucent or glows or may distort the image on the other end.

How does sand become clear glass? The melted silicon dioxide filters away any and all impurities. While sand has impurities that render it visible, pure silicon dioxide forms a robust crystal which is clear glass. Why is glass transparent and brittle? Pure metals reflect light but do not transmit it, because they are filled with free electrons. These electrons reradiate the light in the direction opposite from which it arrived reflection , but they interfere with the light that would proceed in the forward direction, preventing transmission.

She adds some details about the role of physical structure: "A material appears transparent when it does not strongly absorb or diffract light. As far as the absorbance of a solid goes, you pretty much have to take what Nature gives you. Diffraction, however, can be influenced by how the material is prepared.

The boundaries between these regions are called grain boundaries. If the distance between boundaries is smaller than the shortest wavelength of visible light in other words, if the refractive index of the material is uniform with respect to the light passing through it , then the material will appear transparent. Each boundary tends to diffuse the light that passes through; if the regions are small enough, however, the light waves essentially 'jump' right over them.

It has no internal grain boundaries, and hence it looks transparent.