Fresnel’s equations can be used to calculate the polarization of reflected light by providing the reflection coefficients for both polarization components of incident light:
- s-polarized light (electric field perpendicular to the plane of incidence)
- p-polarized light (electric field parallel to the plane of incidence)
These reflection coefficients indicate how much of each polarization component is reflected at an interface between two media with different refractive indices, depending on the angle of incidence.
Here’s how Fresnel’s equations help in determining the polarization of reflected light:
- Different Reflection Strengths:
The amount of reflected light is different for s- and p-polarizations. Fresnel’s equations show that s-polarized light is usually reflected more than p-polarized light at non-normal incidence. - Partial Polarization:
If the incident light is unpolarized, meaning it contains equal amounts of s- and p-polarization, the reflected light becomes partially polarized. This happens because one polarization component reflects more strongly than the other. - Complete Polarization at Brewster’s Angle:
Fresnel’s equations reveal that at a specific angle called the Brewster angle, the reflection coefficient for p-polarized light becomes zero. As a result, only s-polarized light is reflected, and the reflected beam is completely polarized perpendicular to the plane of incidence. - Determining Degree of Polarization:
By comparing the reflected intensities of s- and p-polarized components (using the square of their reflection coefficients), one can calculate the degree of polarization of the reflected light. This is useful in applications like photography, remote sensing, and optical filtering.
Therefore, Fresnel’s equations not only describe how much light is reflected but also how its polarization changes upon reflection, allowing precise control and analysis of polarization in optical systems.