Polarization Ellipse: Understanding 2*Psi Angle

In summary, the orientation angle of an ellipse in radio astronomy is typically expressed as tan(2 * Psi) = S2/S1, where S2 and S1 are the stokes parameters. This factor of 2 is included to make the functions periodic over 180 degrees instead of 360 degrees, allowing for the polarization vector to be rotated by 180 degrees and still describe the same ellipse. This is similar to rotating polarizers by 90 degrees and getting the same result.
  • #1
Steleo
13
0
Hello all

In radio astronomy the orientation angle of an ellipse is usually quoted as
tan(2 *Psi) = S2/S1

Where S2 and S1 are the stokes parameters.

Does anyone know or can point me to a reference as to why the 2 * psi should be in there? The angle of the axis in the ellipse should be able to go between -Pi/2 to Pi/2? Does it have something to do with the fact that you can rotate all your polarisers by 90 degrees and get the same result?

Cheers
 
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  • #2
http://en.wikipedia.org/wiki/Stokes_parameters

If you take the polarization vector and rotate it 180 degrees, you are describing the same ellipse. That's where the factor of 2 comes from, to make those functions periodic over 180 degrees instead of 360 degrees. Not sure if that's exactly what you were talking about when you said rotate both of your polarizers 90 deg., but it's the same idea.
 
  • #3



Hi there,

The 2*Psi angle in the polarization ellipse is related to the Stokes parameters and is a measure of the polarization angle of the electromagnetic wave. It is defined as the angle between the major axis of the ellipse and the horizontal axis, and it can range from -Pi/2 to Pi/2 as you mentioned.

The reason for including the 2*Psi in the equation is due to the fact that polarization is a vector quantity and can have both magnitude and direction. By using the Stokes parameters, we can fully describe the polarization state of the electromagnetic wave. The 2*Psi angle is important because it helps us understand the orientation of the polarization ellipse, which is crucial in determining the polarization properties of the wave.

As for the rotation of polarizers, you are correct in that rotating them by 90 degrees will result in the same polarization state. This is because the 2*Psi angle is only a measure of the orientation of the ellipse, not the magnitude or direction of the polarization itself.

I hope this helps clarify the role of the 2*Psi angle in understanding the polarization ellipse. For more information, I suggest looking into books or articles on polarization in radio astronomy. Best of luck in your research!
 
1.

What is a polarization ellipse and why is it important in science?

A polarization ellipse is a graphical representation of the polarization state of light. It is important in science because it helps us understand how light behaves and interacts with different materials, which has applications in fields such as optics, materials science, and astronomy.

2.

How is the 2*Psi angle related to polarization ellipse?

The 2*Psi angle, also known as the ellipticity angle, is an important parameter in the polarization ellipse. It describes the tilt of the major axis of the ellipse and helps determine the degree of elliptical polarization of the light.

3.

What factors affect the 2*Psi angle in a polarization ellipse?

The 2*Psi angle can be affected by the properties of the incident light, such as its wavelength and polarization direction. It can also be influenced by the material it passes through, such as its refractive index and thickness.

4.

How can the 2*Psi angle be measured in an experiment?

The 2*Psi angle can be measured using polarimetry techniques, which involve analyzing the changes in the polarization state of light as it passes through a sample. This can be done using specialized instruments such as polarimeters or with simple setups using polarizing filters.

5.

What are the practical applications of understanding the 2*Psi angle and polarization ellipse?

Understanding the 2*Psi angle and polarization ellipse has many practical applications in science and technology. It is used in the development of optical devices such as polarizers, waveplates, and filters. It also plays a role in remote sensing and imaging techniques, as well as in the study of the properties of materials and their interactions with light.

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