Wave Optics

A beam of unpolarized light passes through a tourmaline crystal A and then it passes through a second tourmaline crystal B oriented so that its principal plane is parallel to that of A. The intensity of emergent light is \(I_0\). Now B is rotated by \(45^{\circ}\) about the ray. The emergent light will have intensity \(\left(\cos 45^{\circ}=\frac{1}{\sqrt{2}}\right)\)