1. UNIVERSITY OF LUCKNOW
Department of chemistry
SESSION-2024-2025
PROJECT AND SEMINAR REPORT
Interaction of EMR with matters
SUBMITTED BY
•VISHAL SINGH
•ROLLNO : 2410014175040
•M.Sc.( CHEMISTRY) 2nd
SEM.
•SUPERVISION OF
•DR. JOY SARKAR
2. Electromagnetic radiation
Visible light is a form of energy. It was believed that light travels is a straight line. But, this
concept could not explain the some important phenomena like;
Interference
Refraction
Diffraction
To explain the above phenomena, light is supposed to travel in waves. The property of light is
best explained by two complementary theory;
1. Corpuscular theory: it explains the particle nature of light (Compton effect and photoelectric effect)
2. Wave theory : it explains the wave nature of light (diffraction, interference, refraction)
Visible light is a form of electromagnetic radiation. Other forms of electromagnetic radiations
are;
-rays, X-rays, Ultra-violet, Infra red (Near and Far IR), Microwave and Radio waves
These electromagnetic radiation are classified according frequency and wave
length or wave number.
3. Characteristics of Electromagnetic radiation
Important characteristics of electromagnetic radiation are;
These are produced by the oscillation of electric field and magnetic field. The electric and
magnetic field components are mutually perpendicular to each other as well as
perpendicular to the direction of propagation of photon.
4. These are characterized by their frequency, wave length or wave number
The energy carried by an electromagnetic radiation is directly proportional to its frequency. The
emission or absorption of radiation is quantized and each quantum of radiation is called photon.
Εαυ
or E = hυ (where, h is Plank's constant)
or E = hc/ λ 'c' is the velocity of light and‘’
λ is wave length of radiation
All types of radiation travel with the same velocity and no medium is required for their
propagation. They can travel in the in vacuum also .
When visible light (group of electromagnetic radiation) is passed through a prism, it splits
into seven (VIBGYOR) colour having corresponding wave length. This phenomena is
called dispersion.
5. Interaction od Electromagnetic Radiation with Matter
Matter may be either atoms or molecules
All the electromagnetic radiations contains two components;
- Electric field component
- Magnetic field component
The study shows that the interaction between the radiation's magnetic field and atom's charges is much
weaker than the interaction between radiation's electric field and atom's charges. So, in the interaction
of electromagnetic radiation with matter, the role of electric field component is dominating.
However, in NMR spectroscopy the interaction takes place between magnetic field dipole moment
of nuclei and the radiation's magnetic field. The interaction of electromagnetic radiation with matter
results the molecular spectroscopy or electromagnetic spectrum. After interaction, there exists;
• Absorption
• Emission
• Transmission
• Reflection
• Refraction
• Dispersion
• Polarization
• Scattering
6. Absorption of Electromagnetic Radiation
The electromagnetic radiation when interact with matter or substance, it may totally or partially
absorbed by the matter.
In the process, energy is transferred to the absorbing molecule and electrons move from lower
energy state to higher energy state.
The amount of energy absorbed is equal to the energy difference between the two energy levels.
Also, it is evident that not all the incident radiations are absorbed by molecules.
Only those incident radiations, which exceed certain specific value called threshold energy, can
be absorbed at atomic or molecular level.
7. Emission of Electromagnetic Radiation
Emission is the process in which the energy of photon is released by an atom. In the process, electrons
are returned back from higher energy state to the lower energy state.
Transmission of Electromagnetic Radiation
Transmission always occurs in radio wave regions.
We know that radio waves are electromagnetic radiations.
These waves are used for wireless transmission of sound massages or information as well as
communication for marine and aircraft navigation.
The information is imposed in the form of electromagnetic carrier wave as amplitude modulation (AM)
or as frequency modulation (FM) or in the form of digital (pulse modulation).Therefore, in
transmission, there is no single frequency electromagnetic wave.
It involves a frequency band, whose width is proportional to the information density.
The width is about; 10,000 Hz for Telephone
20,000 Hz for high field sound
5 M Hz for high definition television
8. Scattering of Electromagnetic Radiation
When an electromagnetic radiation like light strikes the atom,
it scattered in all possible directions in space. the scattering is
represented in the figure below;
A large number of atoms, when arranged in a perfect periodic array in three
dimensional space to form a crystal, scattering of electromagnetic radiation takes
place in a certain direction. This type of scattering is known as diffraction. Thus,
diffraction is only a special kind of scattering.
9. THANK YOU VERY MUCH
Project finalized under the supervision of
Dr. Joy Sarkar
