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Does absolutely all visible light pass through the atmosphere? Why or why not?

What lets some electromagnetic waves pass through and not others?

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  • $\begingroup$ Rayleigh scattering $\endgroup$
    – LedHead
    Commented Feb 24, 2017 at 1:04
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    $\begingroup$ -1. No research effort. $\endgroup$ Commented Feb 25, 2017 at 3:24

3 Answers 3

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There are three main components to opacity in the Earth's atmosphere at visible wavelengths.

These are:

Rayleigh scattering of light by atoms and molecules. This affects light of all wavelengths, but has a $\lambda^{-4}$ dependence, so is strongest in the blue/UV.

Aerosol scattering caused by particulates and dust in the atmosphere. This affects all wavelengths and has quite a flat wavelength dependence.

Absorption of light by molecules, particularly oxygen and water is particularly effective at discrete wavelengths and bands, primarily in the red part of the visible spectrum, although absorption by ozone ramps up sharply at UV wavelengths and effectively defines a short-wavelength cut-off in atmospheric transmission at $\sim 300$ nm.

The typical amount of light that makes it to the ground through the atmosphere depends on the atmospheric conditions (humidity, dust content etc) and of course how high you are and the angle at which you are looking. At zenith, at a good astronomical site then roughly 10% of light is absorbed at red wavelengths (but with discrete, molecular bands superimposed), rising to 20% in the blue and 50% and upwards in the violet.

The plot below is the transmission measured for the site of the VLT in Paranal (very little aerosol pollution).

Transmission at Paranal

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Well you don't need any complicated answer at all. Just think about sunrise and sunset - absorption of blue light - to display an array of red colour.

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The light that makes it through scatters, especially during a sunset. Most of the UV light is blocked by the atmosphere, but because of light scattering during the day, the sky appears blue, and the sun appears yellow, even though it is actually white.

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