Correct Answer - C
Plane-polarized light (used in the analysis of enantiomers) is produced in an instrument called a polarimeter (polariscope) and passes thorugh a polarimeter tube holding either the liquid enantiomer or its solution. The angle through which the polarized light has been rotated is measured in an analyzer. The observed rotation `(alpha_(obs))` is expressed in degrees.
If the polarized light plane is rotated to the right (clockwise), the anatiomer is said to be dextrorotatory. A rotation to the (counterclockwise) is called levorotatory. The symbols `(+)` and `(-)` desginate rotation to the right and left, respectively.
Note that polarimeter consist of a light source, two lenses (polarizer and analyzer) and between the lenses a tube to hold the substance that is being examined for optical activity. A periscope is device for viewiing objets that are above the eye-level of the observer or are placed so that direct vision is obstructed.
