It is defined as the measurement and interpretation of the absorbed infrared radiation. This method is mainly used for the identification of chemical substances. The absorption is mainly based on the vibrations of the chemical substances after absorption of the infrared radiation.
The spectrum bands present in the IR spectrum represent the functional groups and bonds present in the chemical substance. Hence, the IR spectrum is commonly known as the finger print of the chemical substance.
The IR region is in between 0.8 and 1,000 μm. Then these regions are again classified into three subclasses. They are as follows: