Imagine a pair of crossed polarizers with transmission axes vertical and horizontal. The beam emerging from the first polarizer has flux density I₁, and of course no light passes through the analyzer (i.e., I₂ = 0). Now insert a perfect linear polarizer (HN-50) with its transmission axis at 45° to the vertical between the two elements—compute I₂. Think about the motion of the electrons that are radiating in each polarizer.