Dextrorotatory and dextrorotation are terms used in chemistry to describe the direction in which a substance rotates plane-polarized light. When a substance is said to be dextrorotatory, it means that it rotates plane-polarized light to the right or clockwise direction, whereas when it is levorotatory, it rotates plane-polarized light to the left or counterclockwise direction.
The terms "dextrorotatory" and "levorotatory" come from the Latin words "dexter" meaning "right" and "lævus" meaning...
At dawn and dusk, large amount of blue and violet light(shorter wavelength) has been scattered so, the light that is recieved by an observer is mostly of a longer wavelength and therefore appears to be red.

