Biophysics - Electromagnetic Radiation & Nuclei

Biophysics - First Level (2024-2025)

• Course code: FAC-104
• Prepared by: Dr. Nermin Ali and Dr. Enas Lotfy
• Lecture number: 10

Electromagnetic Radiation

• Demonstrates various forms of electromagnetic radiation, including examples from space and imaging technologies.

Nuclei and Particles

• Matter is composed of molecules, which can be separated relatively easily.
• Molecules are formed by atoms, joined by chemical bonds that are more difficult to break.
• Atoms are made of even smaller particles, electrons and nuclei.
• Atoms contain largely empty space, with the nucleus, the positively charged center holding most of the mass.
• Nuclei are composed of protons (positive charge) and neutrons (no charge).

Bohr Atomic Model of a Nitrogen Atom

• A diagram illustrating the structure of a nitrogen atom according to the Bohr model, showing electron orbits, electrons, and protons.
• Neutrons are located in the center of the atom, along with protons.

Nucleus and Atomic Number

• Nucleus: The central part of an atom; protons and neutrons reside here.
• Atomic number (Z): The number of protons in the nucleus of an atom.
• Proton: Positively charged particle found in the nucleus, with approximately 1 atomic mass unit (amu).
• Neutron: Neutrally charged particle in the nucleus, with approximately 1 amu.
• Mass number: The sum of the number of protons and neutrons in the nucleus of an atom.

Radioactivity

• Nuclear decay, or radioactivity, is the process by which an unstable nucleus loses energy by emitting ionizing radiation.
• This property is exhibited by certain types of matter, spontaneously emitting energy and subatomic particles.
• It's a characteristic of individual atomic nuclei.

Types of Radioactive Decay

• Unstable nuclei decompose spontaneously into more stable configurations, by emitting specific particles or forms of electromagnetic energy.
• Common forms include alpha particles (α), beta particles (β), and gamma rays (γ).

Half-life

• Half-life (t_1/2): The time needed for half of the atoms of a radioactive material to decay to another nuclear form.
• Half-life can vary from fractions of a second to billions of years.
• Decay constant (λ): A constant rate of decay for the radioactive material.

Decay Rate

• Decay rate (A): The rate of disintegration of nuclei.
• Decay rate is proportional to the number of nuclei present.

Types of Radioactive Decay

• Alpha decay: Emission of an alpha particle (2 protons + 2 neutrons, equivalent to a helium nucleus). This reduces the atomic number by 2 and the mass number by 4.
• Beta decay: Emission of a beta particle (an electron). This increases the atomic number by 1 while maintaining the mass number.
• Gamma decay: Emission of a gamma ray (high-energy photon). This does not change the atomic number or mass number.

Shielding

• Different materials provide varying levels of shielding against different types of radiation.
  • Paper protects against alpha particles.
  • Wood or plastic offers some protection against beta particles.
  • Concrete, steel, or lead are effective against gamma rays.

Dive into the intricacies of electromagnetic radiation and the fundamental constituents of matter in this biophysics quiz. Explore the Bohr model of the nitrogen atom and the composition of nuclei and particles through detailed examples and diagrams. Prepare to solidify your understanding of these essential concepts in physics!