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I want to know how a ceramic transparency is mostly affected by the pores, grain boundary, second phases etc. present inside of it, but the major contribution is due to the pores.

Let's consider the glass slab with an air gap between them. It is still transparent.

Hence: how can simple pores make ceramics opaque? I am after a theoretical description.

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This is related to What is difference between white objects and transparent objects as far as photons are concerned?. In fact it's awfully close to a duplicate.

Whenever light encounters a refractive index mismatch there will be some reflection, so some of the light will reflect at every ceramic/air interface. In your example of two glass slabs with an air gap between them the system actually isn't transparent because around 15% of the light is reflected and doesn't make it through. You can see this by looking at your reflection in a double glazed window at night. You'll see several reflections, one from each air/glass interface.

When you have many thousands of air pores in a ceramic you get reflection at the surface of every pore, but because the pore surfaces are not coplanar the light is reflected in many different directions and is effectively randomised. The end result is that the ceramic looks white.

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  • $\begingroup$ Thank you sir,i would like to know from wher this exp: I/I0=0.95^n comes . (ques: What is difference between white objects and transparent objects as far as photons are concerned?) $\endgroup$
    – Pratik
    Jun 3, 2014 at 11:36

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