Question

Why zinc oxide and titanium dioxide nanoparticles are transparent? Why something extremely small become transparent?
Is that related to the refacetive index?
Ice is transparent. Snow is white. Can snow be extremely small and be transparent?

Answer 1

The question it self is not correct because not every nanoparticle or small particles are transparent. eg. Carbon Nanoparticles are not transparent.

Yes, Transparancy of any material depends on its refractive index.

T=1-R

where R is reflection

.

hence it is clear that transmission depends on refractive index.

Ice is transparent due to its highly crystalline nature. so its shows very less reflection and appears transparent, where as snow consists of small ice flakes which are not regularly arranged unlike ice crystal hence the light reflects more from its surfaces.

if the snow particles are extremely small and you pack it in densely in small volume so it become like a crystal then it is transparent to light.