ndt lkecvel iiii

1. ASNT NDT Level-III
Radiography Testing(RT)
Chapter 1
Basic Physics of Radiography

2. Basic Physics of Radiography
• Elementary Particles
• The Electron: The electron is a subatomic particle that
carries a negative electric charge. It is one of the fundamental
particles that make up atoms, along with protons and
neutrons. Electrons are extremely small and have a mass of
about 9.11 x 10^-31 kilograms.
• The Proton: The proton is a subatomic particle that
carries a positive electric charge. It is one of the fundamental
particles that make up atoms, along with electrons and
neutrons. Protons are relatively larger and heavier compared
to electrons and have a mass of approximately 1.67 x 10^-27
kilograms.
• The Neutron: The neutron is a subatomic particle that
is electrically neutral, meaning it carries no electric charge. It is
one of the fundamental particles that make up atoms, along
with protons and electrons. Neutrons are slightly more
massive than protons, with a mass of approximately 1.67 x
10^-27 kilograms, which is about the same as a proton's mass.

3. • Atomic Number: The atomic number of an atom represents the number of protons in its nucleus. It is a
unique identifier for each element on the periodic table. For example, hydrogen has an atomic number of 1,
indicating that it has one proton in its nucleus, while oxygen has an atomic number of 8, indicating it has
eight protons.
• Mass Number: The mass number of an atom represents the total number of protons and neutrons in its
nucleus. It is denoted by the symbol "A." For example, carbon-12 has a mass number of 12, indicating it has
six protons and six neutrons in its nucleus. The mass number helps distinguish between different isotopes of
an element, which have the same number of protons but different numbers of neutrons.
• Atomic Weight: Atomic weight is the average relative mass of all the naturally occurring isotopes of an
element, taking into account their abundance. It is usually expressed in atomic mass units (u) or grams per
mole (g/mol). Atomic weight considers the mass of each isotope and its percentage abundance in a given
sample. For example, the atomic weight of carbon is approximately 12.01 u, reflecting the weighted average
of the masses of carbon-12, carbon-13, and carbon-14 in the Earth's crust.
• Isotope: Isotopes are different forms of an element that have the same atomic number (same number of
protons) but differ in their mass number (due to different numbers of neutrons). Isotopes of an element
exhibit similar chemical behavior but may have different physical properties, such as stability or radioactive
decay. For example, hydrogen has three isotopes: hydrogen-1 (with no neutrons), deuterium (hydrogen-2,
with one neutron), and tritium (hydrogen-3, with two neutrons).
Note: Isotopes are denoted using the element's symbol along with the mass number as a superscript.
For example, carbon-14 is written as 14C, where "14" represents the mass number and "C" represents the
element symbol for carbon.
The concept of isotopes is significant in various fields, including nuclear physics, radiometric dating, and
medical imaging, as different isotopes can have distinct applications and properties.

4. Electromagnetic Radiation
• Photon: A photon is the smallest indivisible unit or quantum
of electromagnetic radiation. It behaves both as a particle
and a wave. Photons carry energy and momentum and
interact with matter as discrete particles. They have no mass
but travel at the speed of light. Photons are emitted and
absorbed by atoms during electronic transitions, giving rise
to the various forms of electromagnetic radiation.
• X-ray: X-rays are a type of electromagnetic radiation with
high energy and short wavelengths, falling between
ultraviolet (UV) light and gamma rays in the electromagnetic
spectrum. X-rays have the ability to penetrate matter to
varying degrees, depending on their energy. They are
commonly used in medical imaging (X-ray radiography) to
visualize the internal structures of the human body. X-rays
also find applications in industrial testing, materials analysis,
and scientific research.
• Gamma Ray: Gamma rays are the most energetic form of
electromagnetic radiation, with the shortest wavelengths
and highest frequencies. They are produced during certain
nuclear processes, such as radioactive decay, nuclear
reactions, or high-energy particle interactions. Gamma rays
possess high penetrating power and are capable of ionizing
atoms and molecules. They are extensively used in medical
imaging (gamma-ray imaging) and cancer treatment (gamma-
ray therapy), as well as in scientific research and industrial
applications.
Radioactivity
• Radioactivity refers to the spontaneous emission of radiation
from the nucleus of an unstable atom. It is a natural process
that occurs in certain elements, known as radioactive
elements or isotopes, where the nucleus is not in a stable
configuration.
• Alpha Particle: An alpha particle is a type of particle emitted
during certain forms of radioactive decay. It consists of two
protons and two neutrons, which is equivalent to the nucleus
of a helium atom. Due to their relatively large mass and
charge, alpha particles have low penetrating power and can
be stopped by a few centimeters of air or a sheet of paper.
They are positively charged and can cause ionization in
matter they interact with.
• Beta Particle: A beta particle is a high-energy electron (beta-
minus particle) or positron (beta-plus particle) emitted during
radioactive decay. Beta-minus particles are electrons, while
beta-plus particles are positively charged and similar in
nature to an electron but with a positive charge. Beta
particles have greater penetrating power compared to alpha
particles and can be stopped by a few millimeters of
aluminum. They can cause ionization and have a higher
ability to penetrate matter than alpha particles.

5. Radioactive decay
• Radioactive decay is the
spontaneous process by which an
unstable atomic nucleus undergoes
a transformation, resulting in the
emission of radiation. This process
occurs in certain isotopes of
elements, known as radioactive
isotopes, where the nucleus is not
in a stable configuration.
Radioactive decay can be
characterized by several different
types, including alpha decay, beta
decay, and gamma decay.

6. Different types of radioactive decay include:
• Alpha Decay: In alpha decay, an unstable nucleus emits an alpha particle, reducing its atomic number by two
and its mass number by four.
• Beta Decay: Beta decay involves the emission of a beta particle, either a beta-minus particle (electron) or a
beta-plus particle (positron), resulting in a change in the atomic number of the nucleus.
• Gamma Decay: Gamma decay does not involve the emission of particles but instead releases high-energy
gamma rays, which are electromagnetic radiation of very short wavelengths. Gamma rays accompany other
forms of radioactive decay and are highly penetrating.
Note: Radioactive decay plays a significant role in various scientific fields, including nuclear physics, medicine
(such as radiation therapy and medical imaging), and environmental monitoring. It is also used in radiometric
dating techniques to determine the age of rocks and fossils.
It's important to note that while radioactivity can have harmful effects on living organisms, it also has beneficial applications in various fields,
such as energy generation (nuclear power) and medical treatments.

7. Let's discuss each type of radioactive decay, along
with an example, equation, and formula associated
with them:
• Alpha Decay:
• Example: Uranium-238 (238U) undergoing
alpha decay: 238U → 234Th + 4He
• In this example, a uranium-238 nucleus
(238U) undergoes alpha decay, resulting in
the emission of an alpha particle (4He) and
forming a thorium-234 nucleus (234Th).
• Beta Decay:
• Example: Carbon-14 (14C) undergoing beta-
minus decay: 14C → 14N + β- + νe
• In this example, a carbon-14 nucleus (14C)
undergoes beta-minus decay, leading to the
emission of a beta particle (β-) and an
electron antineutrino (νe). It forms a
nitrogen-14 nucleus (14N).
• Gamma Decay:
• Example: Technetium-99m (99mTc)
undergoing gamma decay: 99mTc → 99Tc+γ
• In this example, a metastable technetium-
99m nucleus (99mTc) undergoes gamma
decay, where it transitions to a lower
energy state by emitting a gamma ray (γ). It
forms a technetium-99 nucleus (99Tc).
The equations above represent the nuclear reactions
during radioactive decay, where the elements and
particles involved are specified. The numbers written
as subscripts and superscripts represent the atomic
mass number (superscript) and the atomic number
(subscript) of the elements and particles.

8. Electromagnetic Spectrum