Malus Law — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Malus Law Describes the intensity of plane-polarized light after passing through a second polarizer (the analyzer). Decompose the incident electric field vector E0 into components parallel and perpendicular to the analyzer axis. The transmitted component is E = E0 cos(theta). Intensity is proportional to the square of the electric field amplitude (I proportional to E 2). Substitute E to get I = k(E0 cos(theta)) 2 = I0 cos 2(theta). The incident light must be perfectly plane-polarized. The angle is measured between the transmission axes of the two optical elements. Assumes no absorption losses within the polarizer material itself besides polarization. Using this law for unpolarized light directly (unpolarized light passing through a polarizer always has its intensity halved, independent of orientation). Confusing the angle theta with the angle to the normal of the surface; it is specifically the angle between axes of polarization.