Why is air invisible?

Conclusion at the bottom. Link to wavelengths.

Why is glass transparent? Answer at the very bottom.

Quotes from answers.yahoo and blurtit:

“Air is a mixture of various gases contributing to the earth’s atmosphere. In general, air consists of molecular Nitrogen (N2) with a volume count of 78%, molecular oxygen (O2) with a volume count of 20%. There are also small amounts of Argon (Ar) with a volume of 1.9%, Neon (Ne), Helium (He), Methane (CH4), Krypton (Kr), Hydrogen (H), Nitrous Oxide (N2O) and Xenon (Xe). Other gases and elements like water vapour (H2O), Ozone (O3), Carbon-dioxide (CO2), Sulphur dioxide (SO2) and Nitrogen dioxide (NO2) are found in variable concentration. The ammonia and hydrogen sulphide are also common constituent of air. Water vapour is the source of all forms of precipitation of water and it acts as an absorber as well as emitter of infrared radiation. Carbon dioxide (in general air concentration level is 20%) is a necessary component for photo-synthesis. Ozone is primarily located in the Stratosphere and is an effective absorber and emitter of infrared radiation.”

“TELL ME THE COLOR OF AIR?”

“Pure air is a mixture of invisible and odorless gases, mainly nitrogen and oxygen with small amounts of water vapor, argon, carbon dioxide, neon, helium and hydrogen.”

“none its just clear unless you go to a polluted area in which the air is grey.”

“The air is colourless.The tint of colour is due to the impurities present in it”

“Can you tell the color of love? Air is similar to love.Both can only be felt.”

“AIR is colorless when its clear n pure as love..
Black when polluted
White in the winter morning whene there is lots of fog….
Blue n Yellow when the candle burns……
Hey all this is just crap……..”

“Lightest white in such a way that it is almost invisible.”

“Why is air invisible?”

“There are two reasons:

1 Air molecules are smaller than the wavelength of visible light. If a molecule or even a small particle is smaller than the the wavelngth of light, that object is “invisible”. Light cannot interact with things that are smaller than the light’s wavelength.

2. The air molecules can absorb some colors from white light, but not enough to create an effect. What I mean is, molecules of oxygen do absorb some specific wavelengths as the electrons in oxygen jump up and down, but these missing wavelegths are too narrow to make an effect. This is called the “absorption spectrum”

Another example: Even though Neon gives off and absorbs red light, the pure gas is clear because the aborption of red is too specific to matter.”

“cuz it is………”

“Air is invisible (at the atmospheric pressure) since the molecules of gases do very weakly interact with visible light)
This means that air does not stop the visible light
If air would be visble, the atmposphere would stop the light from the sun”

“Hi. Air, like water and glass, is visible but nearly transparent in thin layers. Thicker layer become easily visible.”

At the atmospheric pressure, air is not compact enough to be visible. If it were visible it would be white because the particles in the air absorb light from all of the wavelengths of visible light, all the colours human eyes can see, and so all colours are equally absorbed and as in an inverted rainbow all colours will penetrate the atmosphere all the way down to us on the surface as the all-in-one-colour white.

Birds, who are dinosaurs,  generally have 4 types of cones, whereas humans generally have 3. They can see ultraviolet.

This is Saturn in infrared

To clarify:

Most of the molecules in air are too small, less than 400 nm, to reflect visible light, 400-700 nm. Air is only invisible to observers like humans who have this narrow spectrum of vision. Objectively, all molecules are visible to the right observer because light comes in all sizes; photons with infinitely short wavelengths. It’s not an inherent property of air to be transparent, it’s just that humans are not able to detect it through the sense of vision. Oxygen reflects (absorbs and emits) some light and neon reflects red light, which has the shortest wavelength, but in total the effect is so little that we can still see through it, i.e. the more powerful reflection of objects behind the air is what we perceive instead. Water vapour, in the form of mist and clouds, show what happens when the concentration thickens.

So, glass is transparent because photons with wavelengths within the range of visible light have too little energy to excite the electrons of glass molecules. Colour is caused by excited electrons releasing photons of certain wavelengths and they release that energy to get back to their resting state. I don’t know what the answer for air is, but whatever it is it is because of the relationship between electrons and photons and nothing else and to be honest there is little else in the world except nuclei, and of course the structures that are made of these things and the sub-things that make of the things’ own structures .

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3 Responses to “Why is air invisible?”

  1. Franz Says:

    Man, I would love to get some more posts about this topic. Thanks alot.

  2. cacabua Says:

    The reasoning that. Molecule is smaller than light wavelength. Seems. Incomplete. ……. becoz then my question is why we. Can see solid state and liquid state while gas. Is invisible. though molecule size is same

  3. enleuk Says:

    Well, e.g. bromine is a red gas, but it is colourless in its solid crystalline state. Glass and plastic are also see-through. It´s not about which state of matter the molecules are in. Molecules are generally further apart in gases and move faster so one could guess that even colourful gases soon dissipate into invisibility. It could also be that small atoms, too small for the wavelengths of visible light, are more likely to be gaseous because of their small size and their subsequently lower density. Either way, in the case of the atmosphere, it is see-through because of the low density.

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