Haloalkanes and Haloarenes — Chemistry STD 12 Science — Question

→ Stereochemistry is the branch of that involves "the study of the different spatial arrangements of atoms in molecules".
→ Plane polarised light (PPL) when ordinary light is passed through a nicol prism a light of single wavelength vibrating in a single plane is obtained this is known as plane polarised light.

→ Optical activity: "When plane polarised ligh is passed through a solution the light is rotated either in clockwise or in a anticlockwise direction by a certain angle. These types of compounds an known as optical active compound and such property is known as optical activity."
→ The angle by which the plane polarised light is rotated is measured by an instrument called polarimeter.
→ If the compound rotates the plane of plan polarised light to the right, i.e., clockwis direction, it is called dextrorotatory (Greek for right rotating) or the d-form and is indicated by placing a positive (+) sign before the degree of rotation.
→ If the light is rotated towards left (anticlockwis direction), the compound is said to be laevo rotatory or the l-form and a negative (-) sign in placed before the degree of rotation.
→ Such (+) and (-) isomers of a compound an called optical isomers and the phenomenon is termed as optical isomerism.