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I thought to look into the environment for the inspirations, and what could be so easily accessible as a photogenic sensor (a camera)? The diffraction from the lens was the experimental proof for the electromagnetism, and the light ray was bent from the lens or the heat. The cold weather froze and reduced the water molecular from the atmosphere, given the clearest imaging to the moon. It was rather magical to see how the physics worked just as it would, and there's the exercise and the air from the forests.

Something came up rather surprisingly. That was, the amount of the polarized light there was in the environment. It was expected that, the light from the glass and the river might be polarized, and the unpolarized light might be reduced by 50% from the quantum mechanics. However, it turned out, there was more, i.e. way more polarized in the environment than one would previously have thought.

By using a polarized filter, it turned out, half of the light in the atmosphere was polarized. This was especially obvious during the morning or the evening, commonly known by the photographers, that might create unbalanced removal of the light from the sky. But the light from the sky had already refracted with various clouds in rather a randomized way, i.e. the air molecular etc. How could half of the sky be polarized to mostly one direction like that shown on the camera?

That's not all the story. What's more complicated was the light from the forest. One went for a trip to the forest and climbed on a hill at noon, the image from the leaves sometimes looked very much overly exposed. Here's the magic, the light from the leaves was also largely polarized! By adjusting the polarizer to match the angle, the light from the leaves could be reduced and the leaves looked even greener than they looked with the naked eye.

It wasn't surprising to see there's polarized light in the environment, especially if it was in the city or in the lab. But this was the forest, in the wild, and the existing of so much polarized light questions how quantum mechanically the world really was. Instead of expecting the light be mostly saturated to be unpolarized, the reality was rather shocking.

Why is there so much polarized light in the atmosphere?

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The reflected light from the leaves is polarised and the use of a polarising filter can reduce the glare and enhance the colour of the leaves as shown below.

enter image description here

The polarisation of light emanating from the sky is because of Rayleigh scattering which is the scattering of light from particles whose dimensions are much smaller than the wavelength of the light.
The electric field component of light from the Sun causes the charges in the particles responsible for the scattering to oscillate and re-radiate light of the same wavelength in all directions.
The reason the light is polarised can be seen from the diagram below.

enter image description here

Unpolarised light from the Sun hits a small particle in the atmosphere and the light is re-radiated in all directions.
The scattered light is partially polarised but light which is scattered at right angles to the incident light direction, $\theta = 90^\circ$ in the diagram, is plane polarised as the electric field of a light wave cannot oscillate along the direction of propagation of the light.

The blue sky / cloud contrast is enhanced using a polarising filter because the particles in the clouds are much larger than the wavelength of light and the scattered light is not polarised.

enter image description here

The photographs were taken on an iPhone with the polarising filter used for the right hand one.

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    $\begingroup$ Individual water drops in the clouds do polarize scattered light, but there's a lot of multiple scattering that tends to average this effect out. $\endgroup$
    – Ruslan
    Commented Jul 25, 2022 at 23:47

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