Question

Why is light polarized on reflection?

Answer 1

Light:

1. Light is the combination of electric and magnetic fields traveling through space.
2. The vibration of the electric and magnetic fields is perpendicular to each other.
3. We have one plane occupied by the electric field and one plane occupied by the magnetic field and these planes are perpendicular to each other and the direction of travel of light is perpendicular to both.
4. These electric and magnetic vibrations can occur in various planes.
5. Unpolarized Light: A light wave that is traveling in more than one plane is known as unpolarized light.
6. Polarized Light: When the vibration of a wave occurs in only one plane then it is called polarized light.

Polarization:

1. Transforming unpolarized light into polarized light by restricting the vibration of an electromagnetic wave in other planes so that vibrations occur only in a single plane is called polarization.
2. Brewster's Angle: When an unpolarized light is incident on a reflecting surface at a particular angle such that the angle between the reflected ray and refracted ray is $90°$ and reflected light is completely polarized and this angle of incidence is called Brewster's angle.

Explanation:

1. When the light is incident on the interface then the atoms of the second medium temporarily absorb the light. Electrons of atoms start oscillating toward the electric field of refracted ray, which is perpendicular to the refracted light.
2. To form reflected and refracted rays the light is re-emitted by atoms. The direction of electric field vectors in the light is the same in which the electrons were oscillating, and these electric fields are perpendicular to the wave propagation.
3. When the light is incident at Brewster angle then there are no parallel electric field vectors in reflected and refracted rays because the electrons do not oscillate along that direction.
4. In a reflected ray there are no electric field vectors that are parallel to the refracted ray because it is the propagation direction of the wave. The only possible direction is perpendicular to the second medium plane, hence the reflected ray is polarized linearly

Hence, the light is polarized on reflection.