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
radiation
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
• Electromagnetic
radiation includes ϒ
radiation, x –rays, UV – Visible, IR radiations, Microwaves and radio waves.
