What is the relation between mass density and optical density? Is there any relation or are they unrelated?
I’m guessing, by optical density you mean transparent, translucent, and opaque. Well there is clearly some dependency as we can see that when the fog rolls in. A foggy air is more dense (mass density) than clear air all other things equal. And foggy air is less transparent than clear air, which is apparent. Also, the lighter elements tend to be more likely to allow light through than the heavier elements. Silicon, (Si14), the major element in glass, is one of those light elements. Also the natural gases are found on the light end of the element table; and they are pretty much transparent because, compared to solids, they are less dense. So I would say there is a loose relationship wherein less dense materials tend to be more transparent than denser materials. But that is clearly not a tightly bound relationship. For example, water, plain old tap water, is quite dense; yet in its purest form, it’s very transparent. So it’s clear (or transparent) that density is not the only factor deter
Density means how much of something there is per unit volume. Mass is what we usually think of when we say “density”. Optical density is how much light is absorbed passing through a substance. So since light is absorbed by matter, they can be related. On the other hand, in molecular biology we use OD to measure how much DNA/protein is in a solution, where most of the mass is always water.
