Polarized light physics

Nonpolarized light vibrates in different orientations. When nonpolarized light is transmitted through a polarizing filter (filter A), the emerging light becomes polarized (vibrations in one plane). Polarized light that maintains its polarization after interacting with the skin is unable to pass through the cross-polarizing filter (filter B), and hence no light will emerge through the cross-polarized filter and the observer will see no structures. Polarized light that interacts with deeper parts of the skin undergoes multiple scattering events resulting in randomization of polarization. The scattered light emerging from the skin that is in the same plane as the cross-polarized filter (filter B) will pass through the filter allowing the observer to recognize structures.