Two Polaroids P1 and P2 are placed with their axis perpendicular

Two Polaroids P₁ and P₂ are placed with their axis perpendicular to each other. Un polarised light I₀ is incident on P₁. A third Polaroid P₃ is kept in between P₁ and P₂ such that its axis makes an angle 45° with that of P₁ . The intensity of transmitted light through P₂ is

According to malus law, I = I₀cos² θ

I₁ =	I₀
	2

I₂ =	I₀	cos²45°
	2

	I₀	×	I	=	I₀
	2		2		4

I₃ =	I₀	cos²45°
	4

I₃ =	I₀
	8