Question

What is the principle of IR spectroscopy?

• A. absorption
• B. emission
• C. adsorption
• D. AAS

Hint:

Most standard molecular spectroscopies (UV-Visible, Infrared, NMR) are absorption-based spectroscopies.
They measure the decrease in transmitted light intensity due to energy absorption by the sample molecules.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the fundamental physical principle on which Infrared (IR) spectroscopy operates.

Step 2: Detailed Explanation:

• Infrared (IR) spectroscopy is a widely used analytical technique for identifying functional groups in organic and inorganic compounds.

• When molecules are exposed to infrared radiation, they interact with the light.

• If the frequency of the incident IR radiation matches the natural vibrational frequency of a molecular bond (which must have a changing dipole moment), the molecule absorbs a portion of the radiation.

• This absorption excites the molecule from a lower vibrational energy state to a higher vibrational energy state.

• The instrument detects the specific wavelengths of IR radiation that have been absorbed by the sample, producing an absorption spectrum.

• Since the operating technique is based on measuring the absorbed light as a function of wavelength, its fundamental principle is absorption.

Step 3: Final Answer:
The fundamental principle of IR spectroscopy is absorption.