Question about polarization of light by scattering in the atmosphere

In summary: However, if the unpolarised source radiates a wave polarized in the x direction, the electrons in the scatterer will only vibrate in the x direction and will not radiate in the y direction.
  • #1
annamal
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My book says:
Screen Shot 2022-06-01 at 3.40.15 PM.png


I don't understand why the bottom eye only sees the horizontal red arrow and not the other angles (black arrows)
 
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  • #2
The diagram is very confusing. Let's call the direction of propagation z, x is the plane of the paper and y is normal to the paper.
A component of the unpolarised source lying in the y direction will cause an electron in the scatterer to vibrate also in the y direction. It will then radiate all round in the x plane, and you will see it from the bottom location.

However, if the unpolarised source radiates a wave polarised in the x direction, it will cause an electron in the scatterer to vibrate in the x direction also. The electron is then end-on to the bottom observer and does not radiate in that direction.
So the bottom observer sees only those waves from the source having components in the y direction, and which are therefore polarised.
 
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  • #3
Tested experimentally now with polarization filter on a blue sky. Effect is real - visible as fuzzy blackening in the arc roughly perpendicular to the direction to Sun.
 
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  • #4
Remember the plane of polarisation aligns with the circumference of the arc, so rotates as you go around this halo.
 
  • #5
tech99 said:
The diagram is very confusing. Let's call the direction of propagation z, x is the plane of the paper and y is normal to the paper.
A component of the unpolarised source lying in the y direction will cause an electron in the scatterer to vibrate also in the y direction. It will then radiate all round in the x plane, and you will see it from the bottom location.
What is the scatterer?
tech99 said:
However, if the unpolarised source radiates a wave polarised in the x direction, it will cause an electron in the scatterer to vibrate in the x direction also. The electron is then end-on to the bottom observer and does not radiate in that direction.
How do you radiate a wave polarized in the x direction?
tech99 said:
So the bottom observer sees only those waves from the source having components in the y direction, and which are therefore polarised.
 
  • #6
In reply to post #5, the scatterers in the atmosphere are particles of dust and gas molecules.
Waves polarised in the x direction will be present in "unpolarised" sunlight - it is when the electrons vibrate in the plane of the paper.
 
  • #7
tech99 said:
The diagram is very confusing. Let's call the direction of propagation z, x is the plane of the paper and y is normal to the paper.
A component of the unpolarised source lying in the y direction will cause an electron in the scatterer to vibrate also in the y direction. It will then radiate all round in the x plane, and you will see it from the bottom location.
What do you mean by "It will then radiate all round in the x plane"
 
  • #8
If electrons in the scatterer vibrate normal to the paper, they will radiate in all directions in the plane of the paper. It is similar to the radiation from a vertical antenna.
 

Related to Question about polarization of light by scattering in the atmosphere

What is polarization of light?

Polarization of light refers to the orientation of the electric field of a light wave. A light wave is considered polarized when the electric field oscillates in a specific direction, rather than in all directions.

How does light become polarized?

Light can become polarized through various processes, such as reflection, refraction, and scattering. When light interacts with a surface or medium, the electric field can be aligned in a specific direction, resulting in polarization.

What is scattering of light in the atmosphere?

Scattering of light in the atmosphere refers to the process in which light interacts with particles in the air, causing it to change direction and spread out in different directions. This is why the sky appears blue, as blue light is scattered more than other colors in the visible spectrum.

How does scattering in the atmosphere affect polarization of light?

Scattering in the atmosphere can affect the polarization of light by changing the orientation of the electric field. This can result in partially or fully polarized light, depending on the angle and type of scattering.

Why is understanding polarization of light by scattering important?

Understanding polarization of light by scattering is important for various applications, such as remote sensing, atmospheric science, and optical communications. It can also provide insights into the composition and behavior of particles in the atmosphere.

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