Undergraduate
  1. Classical mechanics  1.1. dynamics  1.1.1. Motion in one dimension  1.1.2. Motion in two dimensions  1.1.3. projectile motion  1.1.4. Relative speed  1.1.5. Uniform circular motion  1.1.6. Non-uniform circular motion  1.1.7. Reference frames and transformations  1.2. Newton's Laws of Motion  1.2.1. First law of motion  1.2.2. Second law of motion  1.2.3. Third Law of Motion  1.2.4. Applications of Newton's Laws  1.2.5. Friction and its types  1.2.6. Free Body Diagram  1.2.7. Constraints and pseudo-forces  1.3. Work and Energy  1.3.1. work done by the force  1.3.2. Work–energy theorem  1.3.3. Kinetic energy  1.3.4. Potential energy in classical mechanics  1.3.5. Conservative and non-conservative forces  1.3.6. Energy Conservation  1.3.7. Power and efficiency  1.4. Speed and collisions  1.4.1. Linear momentum  1.4.2. Conservation of momentum  1.4.3. Impulse and impact force  1.4.4. Elastic and inelastic collision  1.4.5. Center of mass and speed  1.4.6. Rocket Propulsion  1.5. Rotational motion  1.5.1. Torque and Angular Momentum  1.5.2. Moment of inertia  1.5.3. Rotational Kinematics  1.5.4. Rotational Energy  1.5.5. Rolling Motion  1.5.6. Precession and gyroscopic motion  1.6. Gravitational force  1.6.1. Newton's law of universal gravitation  1.6.2. Gravitational potential energy  1.6.3. Orbital mechanics  1.6.4. Kepler's laws of planetary motion  1.6.5. Gravitational field and potential  1.7. Fluid mechanics  1.7.1. Pressure and Pascal's Principle  1.7.2. Buoyancy and Archimedes' principle  1.7.3. Fluid Dynamics and Bernoulli's Principle  1.7.4. Viscosity and Poiseuille's law  1.7.5. Surface tension and capillarity  1.8. Oscillations and waves  1.8.1. Simple Harmonic Motion  1.8.2. Damped and driven oscillations  1.8.3. Coupled oscillations and common modes  1.8.4. Wave properties and types  1.8.5. Sound Waves and the Doppler Effect  1.8.6. Wave interference and superposition
  2. Electromagnetism  2.1. Electrostatics  2.1.1. Electric charge and properties  2.1.2. Coulomb's law  2.1.3. Electric field and electric potential  2.1.4. Gauss's Law  2.1.5. Capacitance and Dielectric  2.1.6. Electric dipole and potential energy  2.2. Electric circuits  2.2.1. Current and Resistance  2.2.2. Ohm's law  2.2.3. Kirchhoff's Laws  2.2.4. RC Circuit  2.2.5. AC Circuits and Reactance  2.2.6. Electric power and energy  2.3. Magnetism  2.3.1. Magnetic Fields and Forces  2.3.2. Ampere's Law  2.3.3. Magnetic dipole moment  2.3.4. Biot-Savart law  2.3.5. Magnetic Materials and Hysteresis  2.4. Electromagnetic induction  2.4.1. Faraday's Law  2.4.2. Lenz's law  2.4.3. Self and mutual induction  2.4.4. Transformers and Inductive Circuits  2.5. Maxwell's equations  2.5.1. Gauss's law for electricity  2.5.2. Gauss's law for magnetism  2.5.3. Faraday's law of induction  2.5.4. Ampere-Maxwell law  2.5.5. Electromagnetic waves
  3. Thermodynamics  3.1. Laws of Thermodynamics  3.1.1. Zeroth law of thermodynamics  3.1.2. First law of thermodynamics  3.1.3. Second Law  3.1.4. Third Law  3.2. Heat and work  3.2.1. Heat transfer (conduction, convection, radiation)  3.2.2. Thermal expansion  3.2.3. Heat engines and refrigerators  3.2.4. Carnot cycle and efficiency  3.3. Statistical mechanics  3.3.1. Maxwell–Boltzmann distribution  3.3.2. Entropy and Probability  3.3.3. Partition function  3.3.4. Fermi–Dirac and Bose–Einstein statistics
  4. Optics  4.1. Geometrical Optics  4.1.1. Reflection and Refraction  4.1.2. Mirrors and lenses  4.1.3. Optical Instruments  4.1.4. Fermat's principle  4.2. Wave optics  4.2.1. Interference in wave optics  4.2.2. Diffraction  4.2.3. Polarization  4.2.4. Coherence and holography
  5. Quantum mechanics  5.1. Wave–particle duality  5.1.1. Blackbody radiation in wave–particle duality in quantum mechanics  5.1.2. Photoelectric effect  5.1.3. Compton scattering  5.1.4. De Broglie wavelength  5.2. Schrödinger Equation  5.2.1. Time-independent Schrödinger equation  5.2.2. Particle in a box  5.2.3. Quantum Tunneling  5.2.4. Potential wells and obstacles  5.3. Quantum States  5.3.1. Wave function  5.3.2. Quantum operators  5.3.3. Heisenberg uncertainty principle  5.3.4. Angular momentum and spin
  6. Relativity  6.1. Special relativity  6.1.1. Lorentz transformations  6.1.2. Time expansion and length contraction  6.1.3. Relativistic energy and momentum  6.2. General relativity  6.2.1. Principle of Equivalence  6.2.2. Schwarzschild metric  6.2.3. Gravitational waves  6.2.4. Black holes and event horizons
  7. Solid state physics  7.1. Crystal structure  7.1.1. Bravais lattices  7.1.2. X-ray diffraction  7.1.3. Band theory  7.1.4. Phonons and lattice vibrations  7.2. Electrical and Magnetic Properties  7.2.1. Conductors, Semiconductors and Insulators  7.2.2. Superconductivity  7.2.3. Hall effect
  8. Nuclear and particle physics  8.1. Atomic Structure  8.1.1. Atomic Model  8.1.2. Nuclear binding energy  8.2. Radioactivity  8.2.1. Alpha, beta, gamma decay  8.2.2. Half life  8.2.3. Nuclear Fission and Fusion  8.3. Particle physics  8.3.1. Standard Model  8.3.2. Quarks and Leptons  8.3.3. antimatter  8.3.4. Fundamental interactions
  9. Astrophysics and cosmology  9.1. Stellar evolution  9.1.1. Star formation  9.1.2. Black holes and neutron stars  9.1.3. White dwarfs and supernovae  9.2. Cosmology  9.2.1. The Big Bang Theory  9.2.2. Dark matter and dark energy  9.2.3. Cosmic microwave background

Undergraduate → Nuclear and particle physics → Radioactivity ↓


Nuclear Fission and Fusion


Introduction

Nuclear reactions are at the heart of energy production and are the fundamental processes that power the sun and stars. In nuclear physics, two main types of nuclear reactions can release energy: fission and fusion. This document will explore these processes, their mechanisms and applications in a simple and understandable way.

Understanding the Atom

Atoms are the smallest units of matter that retain the properties of an element. An atom consists of a nucleus made up of protons and neutrons, collectively known as nucleons, surrounded by a cloud of electrons. The nucleus is small compared to the entire atom but contains almost all of the atom's mass.

Nucleus electron cloud

Nuclear fission

Nuclear fission is a process in which a heavy nucleus splits into two or more smaller nuclei, releasing a few neutrons and a large amount of energy. Fission can occur naturally or be induced by particles such as neutrons.

The process of fission

When a neutron collides with a heavy nucleus such as uranium-235, it becomes unstable. This instability causes the nucleus to split into two smaller nuclei, known as fission fragments. This process releases extra neutrons and a large amount of energy:

        ^{235}U + n → ^{92}Kr + ^{141}Ba + 3n + Energy

The energy released in fission is mainly due to the conversion of some of the mass of the nucleus into energy, as described in Einstein's famous equation:

        E = mc²
N ^{235}U ^{92}Crow ^{141}Ba N N N

Chain reaction

In a nuclear reactor, the fission process can become self-sustaining through a chain reaction. When more neutrons are released in each fission event, these can induce further fissions in nearby nuclei. This process is controlled in reactors to maintain a steady power output:

  • In a controlled chain reaction, the number of neutrons that can trigger further fission is limited.
  • In an uncontrolled chain reaction, such as in an atomic bomb, the reaction grows exponentially, releasing massive amounts of energy.

Nuclear Fusion

Fusion is the process in which two lighter atomic nuclei combine to form a heavier nucleus, releasing energy. This reaction powers the Sun and other stars, providing energy in a much more abundant and potentially cleaner way than fission.

The process of fusion

For fusion to occur, the nuclei must overcome their electrostatic repulsion, known as the Coulomb barrier. This requires extremely high temperatures and pressures, as found in the center of stars. For example, in the Sun:

        4^{1}H → ^{4}He + 2e^+ + 2ν + Energy

Fusion reactions release energy because the mass of the resulting nucleus is less than the sum of its parts, and the mass difference is converted into energy.

^{1}H ^{1}H ^{4}he

The challenges of fusion

Fusion promises a nearly unlimited source of energy, but also presents significant technological challenges. Creating the conditions necessary for fusion on Earth requires vast amounts of energy, sophisticated technology to control the plasma, and materials able to withstand the extreme conditions.

Applications of fusion

  • Energy production: Fusion has the potential to provide a sustainable energy source without the radioactive waste produced by fission.
  • Medical uses: Fusion research contributes to advances in plasma physics and technology, which have implications for medical imaging and cancer treatment.

Comparison of Fission and Fusion

Aspect Fragmentation Merger
Fuel Heavy elements like uranium, plutonium Lighter elements such as hydrogen (deuterium, tritium)
Energy release Medium High (per response)
Waste Long term radioactive waste Low level of short-term waste
Current use Widely used in nuclear reactors Experimental (e.g., the ITER project)

Conclusion

Nuclear fission and fusion are compelling processes that present both opportunities and challenges. While fission is currently an established technology for energy production, fusion offers a promising future for clean and abundant energy. Understanding these processes is crucial for advances in nuclear technology and the search for sustainable energy solutions.


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Nuclear Fission and Fusion

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