Radiation Physics and Instruments - Lecture 1

Radiation Physics and Instruments (1)

• Course code: RIRP202
• First Semester-2025
• Instructor: Prof. Dr. Yasser Rammah
• Lecture 1: October 1, 2024
• Topic: Radiation and Atom

What is Radiation?

• Radiation is energy traveling through space.
• Sunshine is a common form of radiation.
• Radiation delivers energy, light, heat, and suntans.
• Humans control exposure to radiation, but still receive small doses from space, air, and earth.
• Ionizing radiation can damage matter, especially living tissue, and is dangerous at high levels.

The Atom

• All matter is made up of atoms.
• Atoms are the smallest components of elements and are composed of protons, neutrons, and electrons.
• Atoms are mostly empty space.
• Protons and neutrons are in the nucleus.
• The number of electrons equals the number of protons.
• Electrons orbit the nucleus.
• A teaspoon of water contains many more atoms than the Atlantic Ocean's teaspoons of water.
• Particle properties (proton, neutron, electron) include symbol, mass in kg, mass in MeV, and charge.

Standard Nuclear Notation

• Mass number (A) = number of protons (Z) + number of neutrons (N)
• Atomic number (Z) = number of protons
• Example notations: 12C6, 13C6, 14C6

Let's Practice (Examples of Calculations, using the above concepts)

• How many protons are in 1H? 1
• How many neutrons are in 3Li4? 4
• How many protons are in 8O17? 8
• How many neutrons are in 1H1? 0

The Nucleus

• Nucleons are particles found in the nucleus (protons and neutrons).
• The nucleus contains most of an atom's mass.
• The total number of protons and neutrons is the mass number.
• The number of protons is the atomic number.
• Isotopes are atoms with the same atomic number but different mass numbers.
• Nuclides are unique atoms.

Atomic Mass Unit (amu)

• Atomic masses can be expressed in grams or amu.
• One mole (6.02 x 10^23 molecules) of a substance has a mass numerically equal to its molecular weight in grams.
• The mass of a single atom can be calculated by dividing the mass of one mole by the Avogadro's number.

Atomic Structure (Diagram referenced)

• The atom contains a nucleus with protons and neutrons.
• Electrons orbit the nucleus within various energy levels (K, L, M.).

Fundamental Particles (Table referenced)

• Properties including symbol, relative charge, mass (amu), and energy equivalent (MeV) for neutrons, protons, electrons, positrons, and alpha particles.

Definitions

• Isotopes: Nuclei with the same atomic number but different neutron numbers and therefore different mass numbers.
• Nucleon: A proton or a neutron.
• Nuclide: A specific nucleus with a given number of protons and neutrons.
• Isobars: Nuclei with the same mass number.
• Isotones: Nuclei with the same neutron number.
• Isomers: Nuclei with the same Z and A, but different energy states (remaining in excited states longer than 10^-5 seconds).
• Mirror Nuclei: Nuclei with the same mass number, where the number of protons in one is equal to the number of neutrons in the other.

Binding Energy

• Binding energy is the energy required to separate a particle from a system of particles.
• Binding energy depends on the shell and the element, increasing with atomic number.

Electromagnetic Wave Duality

• Equations: E = mc², E = hf, c = λf, and E = h/λ
• h is Planck's constant

Electromagnetic Spectrum

• Classification of electromagnetic waves based on wavelength, frequency, and energy.
• Radio waves, infrared, visible light, ultraviolet, X-rays, and gamma rays are examples.

Radiation

• The electromagnetic spectrum displays the energy and wavelength ranges from long radio waves to short gamma rays.
• Ionizing vs. Non-ionizing radiation based on energy levels.

Ionizing vs. Non-Ionizing Radiation

• Ionizing radiation has enough energy to remove electrons from atoms or molecules.
• Non-ionizing radiation does not have enough energy to remove electrons.
• Examples of ionizing radiation are alpha, beta, gamma, X-rays, and neutrons.
• Examples of non-ionizing radiation include radio waves, microwaves, infrared, visible light, and ultraviolet.

Why is it called ionizing?

• Ionizing radiation creates ions (atoms with a charge).
• High-energy radiation removes electrons from atoms.

Penetration Abilities of Radiation

• Different types of radiation have different penetration abilities through materials. (Examples: Alpha is less penetrative than beta, gamma is most penetrative).

Inverse Square Law for Radiation

• Intensity of radiation decreases with the square of the distance from the source.
• Intensity = Power/Area.

Properties Considered When Measuring Ionizing Radiation

• Strength/radioactivity of the radiation source.
• Energy of the radiation.
• Radiation level in the environment.
• Radiation dose/amount.

Units of Radiation

• Roentgen (R): Unit of exposure for electromagnetic radiation.
• Rad: Unit of absorbed dose.
• Rem: Unit of dose equivalent (accounts for different radiation types).
• Curie (Ci): Unit of the decay rate of radioactive materials.
• Electron Volt (eV): Unit of energy.

Practical Units (Absorbed Dose, Equivalent Dose, Effective Dose)

• Absorbed dose: Amount of energy absorbed per unit mass. Measured in Grays (Gy).
• Equivalent Dose: Absorbed dose weighted for the biological effect of different types of radiation. Measured in Sieverts (Sv).
• Effective Dose: Equivalent dose weighted for different organs/tissues sensitivity and response. Measured in Sieverts (Sv).