If air and smoke are both made of atomic particles, why is one transparent & the other opaque?

Question

Air is very dense at sea level so one would imagine that the protons, neutrons & electrons would be close enough together to obscure light.

Answer 1

The air *is* dense enough to block light. Just not light at the wavelengths we use for sight. At many other wavelengths the air is quite opaque. (Particularly wavelengths that correspond to the various energy-level transitions in common air molecules like N2 or O2.)

It's a complicated matter to predict from a substance's molecular structure what wavelengths of light it will absorb/scatter.

Answer 2

Atoms are 99% empty but that hardly matters. The optical properties of any gas/liquid/solid are determined by the way the electrons interact with photons and for all practical purposes electrons dont even have a size. As someone else said air is transparent at visible wavelengths but not at others.

Don't worry about density, glass is more than 1000 times denser than air but still transparent.

Answer 3

Smoke also contains macroscopic particles that make it opaque, unlike clean air, which is made only of atoms and molecules.

Density of the air at the sae level isn't even close to the density needed to obscure light - it can only distort the light (due to the effect that occurs when light enters to the thicker environment) and nothing else.

Answer 4

Smoke is made up of solid particles - we can see solids, hence we can see smoke. Air is made up of all gases which we can't see like oxygen and nitrogen.

Also air is not very dense at see level! And density is referring to how close together molcules are. Molecules are made of atoms joined together which are made of protons, neutrons and electrons - these distances have nothing to do with air density.

Answer 5

Everything is made of atomic particles, called molecules. They all have different properties. A smoke is a solid, dense, floating in air, not dense. The density and crystal packing determine transparency.

Answer 6

because air is a gas and smoke is an aerosol, smoke is air which contains small particles of matter which cause the opacity due to their size.

The larger particles of matter in the smoke absorb the light, wheras in air the smaller and less dense particles merely scatter light. Which allows air to be transparent.

Answer 7

The difference has to do with the different energies required to lift electrons to elevated energy states in air and in the carbon compounds in smoke. These energies are related by Planck's Law to frequencies of electromagnetic energy that are absorbed. In smoke's case, some of these frequencies are in the visible spectrum and some of the light doesn't pass through, making the smoke no longer appear clear.

Answer 8

theres a couple of factors at play here.

first is the size of the peices of matter in smoke compared to that of air. for us to be able to see them, they need to be many more times the size of the molecules and gasses found in air.

second is density of the material. as smoke is ap articulate, its is many many many times more dense that the gaseous state of the air, and this prevent its from being transparent.

Answer 9

Everything is made of atomic particles. So why does anything look like it does? I guess so that it can do the function it was designed for.

Answer 10

molecules are opaque/transpherent to different wavelengths.

our visible wavelength-range is one in which is transparent to air,

our visible wavelength-range was developed to be of a range that is trasparent to air not the other way round,

as for the smoke it is the structure of its molecules that cause it to be opaque to this wavelength range.