Electromagnetic radiation is made up of an electric field and a magnetic field that mutually support each other. It has a dual nature, behaving as waves under some conditions and particles under others. The binding energy of an electron in an atom is the energy required to completely remove it from the atom against the attractive force of the positive nucleus. Left thumb rule describes the direction of magnetic fields around a current carrying wire. Electromagnetic waves have an associated wavelength and frequency, and their velocity equals the product of these. X-rays and gamma rays can behave as particles called photons due to their short wavelengths. Intensity of light decreases with the inverse square of the distance from the source. The document discusses the principles of electromagnetism and properties

1. Electromagnetism and
its Principles
Dr. Ahsaas Blaggan
JR1 (Radiodiagnosis)

2. Electromagnetic radiation is the transport of energy through space as a combination of
electric and magnetic fields.
•Electromagnetic radiations are produced by a charge being accelerated or a charge being
decelerated.
•A magnetic field always surrounds any stream of charged particles.

3. Left thumb rule.
•If a wire is grasped in the left hand
with the thumb pointing in the
direction of the electron current[(-
)to(+)],then the fingers encircling the
wire will indicate the direction of the
magnetic lines around the current.

4. The Electric field has a unique
value and direction at each
point surrounding a charge
• Electric field is sometimes
called the static field because
the charge is at rest.

5. •If the charge moves with a
constant velocity, we not only
see an electric field(E) moving
with the charge, but also
magnetic field (B)surrounding
the line along which the charge
is moving .

6. At constant velocity electric field moves along with the
charge but with acceleration, The charge moves to a
new location before the outer region of the electric
field realize that the charge is at a different place than it
should be.
•The electric field lags behind the charge, as does the
magnetic field. The lagging behind produces a “KINK”
in the electric field lines that move outward from the
charge with a finite velocity.
•We can think of this “kink” as being electromagnetic
radiations.

7. Electromagnetic radiation is made
up of an electric field and a
magnetic field that mutually
support each other.
E and B are perpendicular , they
reverse together , both E and B are
perpendicular to the direction of
propagation.
Energy is transmitted in space by
the EM radiation

8. Left hand rule states that , when you keep
the thumb, Index and middle finger of the
left hand at right angle to each other
,middle finger shows the direction of
current ,index finger shows the direction of
magnetic field, then the thumb will show
the direction of motion.
Left hand rule or dynamo rule.

9. Binding Energy

10. •An atom is described as ionized when one of its electrons has
been completely removed.
•The detached electron is a negative ion and the remnant
atom a positive ion. Together, they form an ion pair.
•The binding energy (E) of an electron in an atom is the energy
expended in completely removing the electron from the atom
against the attractive force of the positive nucleus.
•This energy is expressed in electron volts (eV)

11. • The binding energy
depends on the shell
(EK > EL > EM) and
on the element.
• The energy required
to remove electron
from K shell is more
than the energy
required to remove
electron from the L
shell.

12. WAVE CONCEPT OF
ELECTROMAGNETIC
RADIATIONS

13. •Electromagnetic radiation is propagated through space in the
form of waves.
•Electromagnetic radiations do not need a medium to travel ,
they can be propagated through a vacuum.
•Waves of all types have an associated wavelength and
frequency.
•The wave concept of electromagnetic radiation explains why
it may be reflected, refracted, diffracted, and polarized.

14. • •The distance between the two
successive crest is the wavelength of the
wave, and represented by a symbol
named “LAMBDA” .
• •The number of waves passing a
particular point in a unit of time is called
the frequency, and represented by a
symbol “NU” .
• •If each wave has length lambda, and
nu waves pass a given point in unit time,
velocity is given by
• • velocity=nu x lambda

15. • •Electromagnetic radiations always
travel at the same velocity in a
vacuum.
• •This velocity is (3 X 108 meters per
second), which is usually referred to
as the velocity of light and given the
symbol c. Therefore, we may express
the relationship between velocity,
wavelength, and frequency as-

16. • •Because all types of
electromagnetic radiation have
the same velocity, the frequency
of the radiation must be inversely
proportional to its wavelength.
• • All types of radiation in the
electromagnetic spectrum differ
basically only in wavelength.
• •The wavelength of an
electromagnetic wave determines
how it interacts with matter.

17. Radio waves
•Radio waves have the longest
wavelengths and the least energy of
all electromagnetic waves. There are
different types of radio waves.
Different types of radio waves have
different penetrating abilities and
have different uses. However, their
most common and widespread use is
in communication technologies like
radio, television, mobile phones, etc.

18. Infrared waves
Infrared rays are heat wavesgivenoff by most objects. They
have wavelengthsranging from 1 mm to 700 nm.
Infrared waves cannot penetrate walls. They travel only through line-of-
sight.
Infrared rays are not visible to our naked eyes since we can only see
wavelengths between 380 nm and 740 nm. Around 52% of the energy that
reaches the earth from the sun is Infrared radiation. But they have very high
attenuation. So, we don't use infrared waves for outdoor communication.
Applications of Infrared Rays:- 1. Night Vision Goggles 2.Remote Controls 3.
Homing of missiles 4. Weather forecasting

19. ULTRAVIOLET (UV) RAYS
•Ultraviolet rays (in 'Latin' Ultra means 'Beyond')
have wavelengths ranging from 400 nm to 10
nm. Some small birds have receptors for UV light.
But humans cannot see it.
•UV rays cause suntans and sunburns by making
the body release Melanin in response to the
damage it does to the skin and causes cancer.
•Some materials can glow and fluoresce when
exposed to UV light. Fluorescence is the
phenomenon in which some materials absorb
light of lower wavelengths (For example, UV light)
and emit radiation of higher wavelengths (For
example, visible light).
•Applications of UV rays:- 1. Crime scene
inspection for bodily fluids 2. Detecting presence
of pests in agriculture

20. X-Rays
• X-rays are electromagneticwaves
with wavelengths ranging from 3 nm to
0.03 nm.
• When accelerated electrons hit atoms of
metals(Copper, Gallium, etc.) they make the
electrons in inner orbits leave their orbits. As a
result, the atoms of these metals become
unstable. So, electrons from the outer orbit
move to the inner orbit to stabilize the atom,
thereby releasing an X-ray in the process.
• Applications:-
1. The most common applicationof X-rays is in
creating scans.
2. A CT (Computed Tomography) scan combines
several X-rays (taken at different angles) to
obtain a 3D-image of the body part.
3. X-rays are ionizing. Therefore, radiotherapy
uses X-rays to kill cancerous cells in the
body. Thus, X-rays play a major role in fighting
cancer.

21. Gamma-Rays
• Gamma-rays are very similar to X-rays. However, their
major difference is in the way they are produced.
While X-rays are produced by electrons, Gamma-rays
are produced by nuclei.
• After a radioactive material decays, the resulting
daughter nucleus that is in an excited state releases a
Gamma-ray to reach a stable, low-energy state.
Hence, both nuclear fission and nuclear fusion can
produce Gamma-rays
• Applications
1. Similar to X-rays, the ionizing property of Gamma-
rays is useful in the medical field for killing cancerand
tumour cells.
2. A Gamma knife surgery focuses multiple
concentrated Gamma rays on a cancerous growth from
different angles. Thus, it minimizes damage to healthy
tissues while destroying the cancerous growth.

22. Particle Concept of
Electromagnetic
Radiation

23. •Short electromagnetic waves, such as x rays, may react with
matter as if they are particles rather than waves.
•These particles are actually discrete bundles of energy, and
each of these bundles of energy is called a Quantum, or
Photon. Photons travel at the speed of light.
• The amount of energy carried by each quantum, or photon,
depends on the frequency (v) of the radiation. If the
frequency (number of vibrations per second) is doubled, the
energy of the photon is doubled.

24. The actual amount of energy of the photon may be calculated by multiplying its
frequency by a constant. The constant has been determined experimentally to
be 4.13 X 1018 keV*sec, and is called Planck's constant(h).
•(Planck's constant in SI units is 6.62 X 1034 joules seconds ). Planck's constant
is normally given in the SI units.
•The mathematical expression is written as follows:
•E = hv
•E = photon energy
•h = Planck's constant
•v = frequency.

25. Wave and Quantum theory
combined

26. Product of : H(planks
constant) and C (velocity
of light) is =12.4.​
When the unit of energyis
“keV” and the wavelength
is in “angstroms”. The final
equation showing
the relationship between
energy and wavelength is:

27. •If a photon has 15 e V or more of energy it is capable
of ionizing atoms and molecules, and it is called "ionizing
radiation."
•
•An atom is ionized when it loses an electron. Gamma rays, x
rays, and some ultraviolet rays are all types of ionizing
radiation.

28. Inverse Square Law​

29. •The law states that the intensity of light
from a given source varies inversely with the
square of the distance of the source.
•As the distances increases, the intensity
of the light from the source decreases.

31. UNITS

32. SI BASE AND
SUPPLEMENTARY
UNITS

33. SI DERIVED UNITS WITH SPECIAL NAMES.

34. SUMMARY

35. Electromagnetic radiation is made up of an electric field and a
magnetic field that mutually support each other.
•Electromagnetic radiations They have a dual nature, behaving in some
circumstances as waves and under different conditions as particles.
Therefore, two concepts have been postulated to explain their
characteristics that is the wave theory and the particle theory.

36. •The binding energy (E) of an electron in an atom is the energy expended
in completely removing the electron from the atom against the attractive
force of the positive nucleus.
•Left thumb rule-If a wire is grasped in the left hand with the thumb
pointing in the direction of the electron current[(-)to(+)],then the
fingers encircling the wire will indicate the direction of the magnetic lines
around the current.

37. Wave and Quantum theory.​
• Waves of all types have an associated wavelength and frequency.​
• velocity=nu x lambda​
• The wavelength of an electromagnetic wave determines how it interacts with matter.​
• Short electromagnetic waves, such as x rays, may react with matter as if they are particles rather than
waves.​
• These particles are actually discrete bundles of energy, and each of these bundles of energy is called
a Quantum, or Photon.​

38. •Inverse square law- The law states that the intensity of light from a given
source varies inversely with the square of the distance of the source.
•Units-SI base and supplementary units, SI derived units.

39. References.​
•Christensen’s Physics of Diagnostics Radiology.​
•Farr’s Physics for Imaging.​
•Selman’s the fundamentals of imaging physics
and radiology.​
•Massey and Meredith-Fundamentals physics
of radiology.​

40. Thank You