As light enters the cell, its polarization rotates with the molecules. When the light reaches the bottom of the cell, its polarization vector has rotated by 90 degrees, and now can pass through the second polarizer. In a reflecting TN display, a mirror is placed at the bottom of the cell to reflect the transmitted light. Once again the polarization twists as the light traverses the sample, and is able to emerge from the top of the cell. The following animation shows how light entering the cell twists along the way.
Light emerging from such a cell appears the familiar silver-gray color.
As explained in the Electric and Magnetic Field Effects section, when an electric field of sufficient magnitude is applied to a sample, the molecules undergo a Freederickzs transition. The following animation shows the transition that happened in a twisted nematic cell. Note that in this state, the twist is destroyed. The director of the bulk liquid crystal is parallel to the field and no longer twisted. When polarized light enters a cell in such a configuration, it is not twisted, and is canceled by the second polarizer.