To solve this problem, we need to understand the concept of Brewster's angle.$\\$Brewster's angle, $\theta_B,$ is defined as the angle of incidence at which light is perfectly$\\$polarized upon reflection. At this angle, the reflected and refracted rays are perpendicular$\\$to each other.$\\$The formula for Brewster's angle is given by:$\\ \tan(\theta_B) = \frac{n_2}{n_1} \\$where $n_1$ is the refractive index of the medium from which the light is coming,$\\$and $n_2$ is the refractive index of the medium into which the light is entering.$\\$When unpolarized light strikes a surface at Brewster's angle:$\\$• The reflected light is completely polarized.$\\$• The refracted light is partially polarized, as it still contains components of both$\\$polarizations.$\\$Therefore, the correct option is:$\\$Option 2: The reflected light will be completely polarised but the refracted light will be partially polarised.$\\$This is because at Brewster's angle, the reflected light is polarized perpendicular to the$\\$plane of incidence, while the refracted light retains some degree of polarization parallel$\\$to the plane of incidence.