The Brewster angle is an important concept in wave propagation. It refers to the angle at which a wave is incident on a boundary between two media, such that the reflected wave is completely polarized and the reflection coefficient is zero. In other words, at the Brewster angle, there is no reflected wave.

Explanation:

1. Brewster Angle and Polarization:
- When a wave is incident on a boundary between two media, it can be divided into two components: one that is perpendicular to the boundary (transverse electric or TE wave) and one that is parallel to the boundary (transverse magnetic or TM wave).
- The Brewster angle is the angle of incidence at which the reflected wave is completely polarized and consists only of the TE wave component.
- At this angle, the incident and reflected rays are perpendicular to each other, and the polarization of the reflected wave is such that the electric field is parallel to the boundary.

2. Reflection Coefficient:
- The reflection coefficient is a measure of the amplitude of the reflected wave compared to the incident wave. It is defined as the ratio of the amplitude of the reflected wave to the amplitude of the incident wave.
- In the case of the Brewster angle, the reflection coefficient is zero. This means that there is no reflected wave, and all of the incident wave is transmitted into the second medium.
- Mathematically, the reflection coefficient can be calculated using the Fresnel equations, which describe the behavior of electromagnetic waves at boundaries between media.

3. Significance of Zero Reflection Coefficient:
- The fact that the reflection coefficient is zero at the Brewster angle has important practical implications.
- For example, it can be used to reduce glare and unwanted reflections in optical systems, such as anti-reflective coatings on lenses or windows.
- It is also useful in certain applications, such as polarizing filters, which selectively transmit light of a specific polarization while blocking light of other polarizations.

Conclusion:
- The correct answer to the given question is option 'A' - 0, as the reflection coefficient is indeed zero at the Brewster angle.
- This phenomenon is a result of the polarization properties of the incident and reflected waves, and it has practical applications in various fields.