Radiation Physics and Instruments: Radiation & Atom

Course Information

• Course name: Radiation Physics and Instruments (1)
• Semester: First Semester 2025
• Course code: RIRP202
• Lecturer: Prof. Dr. Yasser Rammah
• Lecture date: 01.10.2024
• 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.
• Exposure to radiation is controlled.
• Higher-energy radiation types exist, used in medicine, and encountered in low doses from space, air, and earth.
• These higher-energy types are collectively known as ionizing radiation.
• Ionizing radiation can damage matter, especially living tissue, and is dangerous at high levels, requiring controlled exposure.

The Atom

• All matter is made up of atoms.
• Atoms are the smallest components of elements, composed of three particles.
• Protons
• Neutrons
• Electrons
• Atoms consist mostly of empty space.
• The atom is neutral.
• Protons and neutrons reside in the nucleus.
• Number of electrons is equal to the number of protons.
• Electrons orbit the nucleus.
• Atoms are extremely small; a teaspoon of water contains more atoms than the teaspoons of water that could fit in the Atlantic Ocean.
• Particle data for proton, neutron, and electron, are included (mass and energy)

Standard Nuclear Notation

• Mass number (A) = number of protons (Z) + number of neutrons (N)
• Chemical symbol (X)
• Atomic number (Z) = number of protons

Let's Practice (Examples)

• Number of protons in 1H? 1
• Number of neutrons in 7Li4 ?4
• Number of protons in 17O8? 8
• Number of neutrons in 1H1?0

The Nucleus

• Nucleons are particles found in the nucleus.
• Protons and Neutrons.
• Atomic Number (Z) = Number of protons.
• Mass Number (A) = Sum of protons and neutrons.
• Isotopes are atoms with identical atomic numbers (Z) but different mass numbers (A).
• A nuclide is a unique atom.

Atomic Mass Unit (AMU)

• Atomic masses can be expressed in grams or unified atomic mass units (u).
• 1 mole of any substance contains Avogadro's number of molecules (6.02 × 10^23).
• The mass in grams of one mole is numerically equal to the molecule's molecular weight.
• Mass of a single atom can be calculated.
• 1 mol of 12C is 12g
• 1 atomic mass unit (amu), also called a dalton, is 1.6605 × 10−24 g.

Electromagnetic Spectrum

• The electromagnetic (EM) spectrum covers a wide range of wavelengths and frequencies.
• Radio waves, Infrared, visible light, UV, X-rays and gamma rays.
• Energy and frequency increase as wavelengths get smaller.

Ionizing vs. Non-Ionizing Radiation

• Non-ionizing radiation lacks sufficient energy to remove electrons from atoms or molecules.
• Ionizing radiation has enough energy to liberate electrons from atoms, resulting in ions.

Why Ionizing Radiation?

• Ionizing radiation creates ions (atoms with a charge) by removing electrons.

Penetration Abilities

• Different types of ionizing radiation have varying ability to pass through matter.
• Alpha particles have the least penetration power; Gamma rays & X-rays penetrate most.
• Neutrins can pass through enormous distances of solid matter.
• Neutrons can penetrate deeper than alpha, beta, x-ray and gamma.

Inverse Square Law

• The intensity of radiation decreases with the square of the distance from the source. (I α 1/r²)

Properties of Ionizing Radiation

• Measured in terms of: source strength/radioactivity, energy of radiation, level of radiation in environment, and the radiation dose/amount of radiation energy absorbed by the human body.

Units of Radiation

• Roentgen (R): Unit for electromagnetic radiation exposure.
• Rad: Unit of absorbed dose; 100 ergs/g (10^-2 Gy).
• Rem: Unit of dose equivalent; traditional unit of dose equivalent or occupational exposure for radiation workers.
• Curie (Ci):Unit used to express the decay rate of a radioactive material (3.7×10^10 atoms disintegration per second).
• Electron Volt (eV): Unit of energy from movement of electrons across an electric potential difference (1.602 × 10^-19 J).

Practical Units

• Gray (Gy): SI unit of absorbed dose (joule per kilogram).
• 1 Gy is equivalent to 100 rad.

Equivalent Dose

• Sievert (Sv): Unit for measuring equivalent dose, considers the absorbed dose and the type of radiation's effect on tissue.
• 1 Sievert = 100 rem.
• Typical units for equivalent dose are millirem or microsievert (10−3 rem or 10−6 Sv).

Effective Dose

• Calculates the overall impact of different types of radiation on various tissues.
• WT: weighting factor used to account for differing tissue damage among different types of radioactive particles.