The Brewster angle is valid for P polarized light.

Explanation:
The Brewster angle is an important concept in optics that describes the angle of incidence at which light is completely polarized when it reflects off a dielectric surface. At this angle, the reflected light becomes completely polarized with the electric field vector perpendicular to the plane of incidence.

To understand why the Brewster angle is valid for P polarized light, let's first define the two types of polarization:

1. S Polarization (perpendicular polarization):
In S polarization, the electric field vector of the incoming light is parallel to the plane of incidence. When light is incident on a dielectric surface at an angle, a portion of it gets reflected and the remaining part gets refracted. The reflected light is partially polarized, meaning it contains both S and P polarized components.

2. P Polarization (parallel polarization):
In P polarization, the electric field vector of the incoming light is perpendicular to the plane of incidence. When light is incident on a dielectric surface, a portion of it gets reflected and the remaining part gets refracted. At a specific angle of incidence known as the Brewster angle, the reflected light becomes completely polarized with only the P polarized component present.

Now, let's look at why the Brewster angle is valid for P polarized light:

- When light is incident on a dielectric surface at the Brewster angle, the reflected light is completely polarized. This means that it contains only one polarization component, either S or P.
- Since the reflected light is completely polarized, it means that the electric field vector of the reflected light is perpendicular to the plane of incidence. This is the characteristic of P polarization.
- At any other angle of incidence, the reflected light is partially polarized and contains both S and P polarized components.
- Therefore, the Brewster angle is valid only for P polarized light.

In summary, the Brewster angle is valid for P polarized light, where the electric field vector is perpendicular to the plane of incidence. At this angle, the reflected light becomes completely polarized with only the P polarized component present.