Hello,

Does someone know how explain what physical feature (molecules arrangement, atoms size, etc) makes an object transparent for visible light ?

Any good explanation is useful.

Thanks.

 

It's to do with photons being the right energy, or wavelength, to excite an electron enough to move up to the next energy shell in the atom. If it does, then the photon is absorbed. . In this case, the medium the photon encountered would be classed as optically opaque. If the photon energy is insuffucient i.e. wrong wavelength, the photon will be momentarily absorbed and then ejected onto the next electron it encounters, which will be repeated until it passes through the other side. If you shone a pure  UVC wavelength - no other light around - at a piece of glass and you took a uv-sensitive photo on the other side, the photo will be black because all the UVC photons have been absorbed. So, to UVC,  glass is opaque but transparent to visible light. It depends on the wavelength what is 'transparent' or not.

Edited February 15, 20187 yr by StringJunky

Here's a more formal description of it: https://en.wikipedia.org/wiki/Transparency_and_translucency

15 hours ago, StringJunky said:

Here's a more formal description of it: https://en.wikipedia.org/wiki/Transparency_and_translucency

Thank you very much. 

Just remember that although SJ referred to electrons in atoms, not many substances apppear in atomic form.

Most appear in molecular form where the atoms are joined together, often many different atoms.

It is some of the atomic electrons that allow this joining and the joins or bonds which are responsible for interacting with the light or not as the case may be.

The arrangement of the particles may be regular as in crystals or jumbled as in grains (referred to in the excellent Wikipedia article SJ offered).

These arrangements are the result of the bonds or joining mechanisms.

 

+1 to SJ for a good answer.

6 hours ago, studiot said:

Just remember that although SJ referred to electrons in atoms, not many substances apppear in atomic form.

Most appear in molecular form where the atoms are joined together, often many different atoms.

It is some of the atomic electrons that allow this joining and the joins or bonds which are responsible for interacting with the light or not as the case may be.

The arrangement of the particles may be regular as in crystals or jumbled as in grains (referred to in the excellent Wikipedia article SJ offered).

These arrangements are the result of the bonds or joining mechanisms.

 

+1 to SJ for a good answer.

Cheers. I wasn't trying to give a comprehensive answer in my first post (i couldn't anyway) but was just trying to get him to see the general, schematic idea of how photons move through a transparent material  with just one type of interaction.