Optics Question: Calculating Degree of Polarization at an Air-Glass Interface

[cuti_pie75]

Here's the question:

a beam of natural light is incident on an air-glass interface (n-ti = 1.5) at 40°. Compute the degree of polarization of the reflected light.

In here, I'm not too sure of the degree of polarization that they're talking about nor which formula to use

Although, i know that the formula for V=(Ip)/(Ip+In) = (Imax-Imin)/(Imax+Imin) but i don't know how i can use this formula, i mean, we don't have the intensity in the pb, the only thing we can find is R// that can be related to I since Ir// = R//Ii/2

(the // means parallel btw) and so far, i figure out all the fresnel coefficient: r//, t//, r (perpendicular) and t(perpendicular). Then don't know what to do next.

Really need help with this...and I'm really lost with what's going on.
Thanx in advance

 

[Claude Bile]

The degree of polarisation refers to the ratio of reflected p and s polarised irradiances. For example a degree of polarisation of 100 means that the reflected p (or s) polarised irradiance is 100 times greater than the reflected s (or p) irradiance.

Claude.

 

[wais]

Hi there,

The degree of polarization refers to the percentage of light that is polarized after interacting with a surface. In this case, we are looking at the degree of polarization of the reflected light at the air-glass interface.

To calculate this, we can use the formula you mentioned, V=(Ip)/(Ip+In), where Ip is the intensity of the polarized component of the light and In is the intensity of the unpolarized component of the light. In this case, we can find Ip by using the formula Ir// = R//Ii/2, where Ir// is the intensity of the reflected light parallel to the incident light, R// is the reflection coefficient for parallel polarization, and Ii is the intensity of the incident light.

To find R//, we can use the Fresnel equations, which you have already calculated. The reflection coefficient for parallel polarization, R//, is equal to (n1cosθi - n2cosθt)^2 / (n1cosθi + n2cosθt)^2, where n1 is the refractive index of the incident medium (in this case, air), n2 is the refractive index of the transmitted medium (in this case, glass), θi is the angle of incidence, and θt is the angle of transmission.

Once we have calculated R//, we can plug it into the formula for Ip, and then use that value to calculate the degree of polarization, V. Keep in mind that for this problem, we are only looking at the reflected light, so we can ignore the transmission coefficient, t//.

I hope this helps clarify things for you. Let me know if you have any further questions. Good luck!