# Thread: (Layman Science Series) Week 8 - Why is silica in glass transparent?

1. ## (Layman Science Series) Week 8 - Why is silica in glass transparent?

Intro
I am trying to post a science/physics question of varying difficulty each week for this year, and maybe a monthly question of greater complexity.

The Rules are:
Answers must be complete, and each statement must be sound/logical.

More than one answer can exists, until its proven false. Hypothesis and theory varies, but scientific logic used must be sound. For example, no marks for cyclic logic. Another example, in cause and effect, no marks for declaring a cause without completely deriving that cause from a generally known and proven fact.

The better the answer, then the more points awarded. Answers can always be updated at anytime as we learn something new everyday.
(I do not claim to have THE answer. I will just attempt to provide a possible answer)

The greater the difficulty, the greater the points. I will give an answer at end of week/month ... hopefully. Repeating my answer awards no points, you will have to come with a better or alternate answer.

I emphasize that Logics is key to getting points aka "Sound logics" aka "there is no other type of logics". It is either logical or illogical. (Some people claim other forms of logic like administrative logistics which they essentially hide some of the steps because such steps are nefarious and then claim that they are using a special type of logics. That will give you zero marks here. Each step must be given) I believe that we are smart people here, so we logically know that "Many people having the same answer" does not automatic conclude, or imply, that that answer is THE answer. What can make an answer THE answer is sound logics and proven experimental tests.)

Question
Why is silica in glass and quartz transparent but in stone and powdered form it is white?

Resources
https://en.wikipedia.org/wiki/Silicon_dioxide
https://en.wikipedia.org/wiki/Quartz

Difficulty
A-Level Physics
A-Level Chemistry

Site share of the week/month

2. Explanation 1
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Thinking in terms of frequency.

A very regular solid with few free election can be transparent because it has a narrow spectrum band

Less electrons --> Less energy level of electrons
Strong bonds --> Less free electrons --> Less energy level of electrons

Less energy level of electrons --> Less spectral lines

Strong bonds --> More regularity (bond are more exact length) --> More exact energy levels --> Narrower spectral lines

Less spectral lines + Narrower spectral lines -->narrow band spectrum absorption --> More transparent

SiO in Glass will be more ordered and thus more transparent with the characteristics above

For non transparency,

First consider a clear plastic cup that you then crush and reshape, you may notice that at the stressed regions, there is a more white translucent color. It is a known phenomena that an antenna with x+1 resonance, if placed close to another antenna with x resonance, both antenna resonances change slightly. It you keep adding more antenna, each resonance is affected by the group. and all may not be at the same level.

In the ordered solid plastic cup, each molecule is in exact placement. Now when the plastic cup is bent, the polymer order is more disrupted, and there is more variation in molecular distance, and changes in the energy levels. Each molecule behaves as an antenna, and each resonant frequency changes slightly. Further more the proximity to other antenna causes more variation. Now there is a broadband interaction with spectral lines and the cup stress regions looses it transparent more narrow band spectral

The same thing with stone, impurities and irregularities in the crystal formation at a bigger level causes a more broadband spectrum

Explanation 2
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Diffraction in orders glass is basic. Visible light pass tru and at most if at an angle there is a rainbow effect but still transparent

In powdered form, micro crystals cause multiple diffractions, thus eventually and effectively reflecting back the light and also mixes back the separated rainbow colors that was reflected, in a random way but still give back a white color

3. This is an example of how atoms' geometry can affect light

Herapathite (iodo sulphate of quinine) is used in the production of : polaroid.
https://brainly.in/question/15576712...the%20quinine.

One of his pupils found that adding iodine to the urine of a dog that had been fed quinine produced unusual green crystals. Herapath noticed while studying the crystals under a microscope that they appeared to polarize light
https://en.wikipedia.org/wiki/Herapathite

Note how the molecule is shaped. I suspect that it is the shape of this substance that mostly gives it its polarizing properties

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