Polarising microscope, plane-polarised light, crossed polars কী?

A polarising microscope is a transmitted light microscope with a polarising filter (the polariser) below a stage that rotates through $360{}^{\circ}$ against a graduated scale, and a second polarising filter (the analyser) between the objective and the eyepiece, which can be moved in or out of the light path, its vibration direction at right angles to the polariser’s. With the analyser out, the specimen is seen in plane-polarised light; with the analyser in, it is seen between crossed polars.