The electric field vector of linearly polarized electromagnetic wave (marked in blue) oscillates only in one direction.  In circularly polarized wave the end of electric field vector (marked in red) moves like a coil.

Light being reflected from the sample surface can change the state of polarization. This phenomenon underlies the principles of ellipsometry.

Microscopy with the use of the principles of ellipsometry. Sample and substrate reflect the light in different polarization. Using polarizer we can visualize the sample and investigate its properties.

If the lineally-polarized light is incident onto the polarizer, then the intensity of the transmitted light will depend upon the angle a between the direction of the light polarization and the orientation of the polarizer.