1) Alter 2) Change 3) Depolarize 4) Modify 1) Depolarize 
1. <optics> To deprive of polarity; to reduce to an unpolarised condition. ... This word has been inaccurately applied in optics to describe the effect of a polarising medium, as a crystalline plate, in causing the reappearance of a ray, in consequence of a change in its plane of polarisation, which previously to the change was intercepted by...