Unpolarized light passes through a polarizer and is polarized linearly in a specific plane. Then this linearly polarized light passes through an analyzer and is now linearly polarized at an angle $$\varphi$$ with respect to the previous polarization. The intensity before passing through the polarizer is $$I_0$$. After passing through the analyzer, the intensity is given by the Malus law and is $$I(\varphi)$$.