Certain materials under the influence ofstrong electric field become doubly refractive. The effect known as Kerr effectcan be observed in this experiment with nitrobenzene solution.
In the present setup, a small glass containermounted with plate capacitor is filled with liquid. The container is kept betweentwo filters placed at 90degree. There will be dark field of view on screeninitially but after applying electric field, the field of view brightens,because the light beam becomes elliptically polarised when passed through thebirefringent liquid.