# Spectroscopy and Electromagnetic Spectrum - Instrumental Methods of Analysis B. Pharma 7th Semester

Spectroscopy and Electromagnetic Spectrum

Session Objectives

By the end of this session, students will be able to:

Ø  Explain the salient features of Electro Magnetic Spectrum

Ø  Outline the parameters for identification and distinction of different Electromagnetic radiations

Spectroscopy

Spectroscopy is the study of the way light (electromagnetic radiation) and matter interact.

There are a number of different types of spectroscopic techniques

The basic principle is to pass a beam of a particular electromagnetic radiation through a sample and observe how it responds to such a stimulus; allowing scientists to obtain information about the structure and properties of matter.

Electromagnetic Spectrum

The electromagnetic spectrum comprises of waves of electromagnetic radiation

The systematic display of whole range of EM wave frequencies is called the electromagnetic spectrum.

Different parts interact with matter in different ways.

The frequencies humans can see are called visible light, a small part of the whole spectrum.

Visible light

 Color Wavelength Violet 400-420 nm Indigo 420-440 nm Blue 440-490 nm Green 490-570 nm Yellow 570-585 nm Orange 585-620 nm Red 620-780 nm

What are electromagnetic waves?

How electromagnetic waves are formed

How electric charges produce electromagnetic waves

Properties of electromagnetic waves

Electromagnetic Waves…

Do not need matter to transfer energy.

Are made by vibrating electric charges and can travel through space by transferring energy between vibrating electric and magnetic fields.

How do moving charges create magnetic fields?

Any moving electric charge is surrounded by an electric field and a magnetic field.

What happens when electric and magnetic fields change?

A changing magnetic field creates a changing electric field.

One example of this is a transformer which transfers electric energy from one circuit to another circuit.

In the main coil changing electric current produces a changing magnetic field

Which then creates a changing electric field in another coil producing an electric current

The reverse is also true.

Making Electromagnetic Waves

When an electric charge vibrates, the electric field around it changes creating a changing magnetic field.

The magnetic and electric fields create each other again and again.

An EM wave travels in all directions.  The figure only shows a wave traveling in one direction.

The electric and magnetic fields vibrate at right angles to the direction the wave travels so it is a transverse wave.

SUMMARY

Spectroscopy is the study of the way light (electromagnetic radiation) and matter interact.

The systematic display of whole range of EM wave frequencies is called the electromagnetic spectrum