Brewster S Law — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Brewster's Law Applies to the reflection of unpolarized light at the interface of two transparent dielectric media. It defines the condition where the reflected light is completely plane-polarized perpendicular to the plane of incidence. Assume unpolarized light strikes an interface at angle i p. Experimental observation: At i p, the reflected ray and refracted ray are perpendicular (90 degrees apart). From geometry: i p + 90 + r = 180, implying r = 90 - i p. Apply Snell's Law: = (i p) / (r). Substitute r: = (i p) / (90 - i p) = (i p) / (i p) = (i p). The medium must be a dielectric (transparent non-conductor). The incident light must be unpolarized. Strictly valid when the incident medium is air/vacuum; otherwise is the relative refractive index (n2/n1). Confusing Brewster's angle (polarization) with the Critical angle (total internal reflection). Thinking the refracted ray is also completely polarized (it is only partially polarized). Assuming the reflected ray vanishes (it does not; it just becomes polarized).