Introduction to Physics: Core Concepts

• Physics examines matter, its basic parts, movement through space-time, and related concepts like energy and force.
• A primary goal of physics is deciphering the universe's behavior.
• Physics, incorporating astronomy, stands as one of the oldest academic fields.
• Progress in physics often spurs new technologies.
• For example, understanding electromagnetism, solid-state physics, and nuclear physics has enabled the creation of transformative technologies like television, computers, appliances, and nuclear weapons.
• Thermodynamics advancements spurred industrialization; mechanics innovations led to calculus development.

Core Concepts

• Physics addresses phenomena from subatomic particles to galaxies.
• It studies matter, energy, space, time, and their interactions.
• Classical physics includes mechanics, thermodynamics, optics, and electromagnetism.
• Modern physics includes quantum mechanics, relativity, and nuclear physics.

Mechanics

• Mechanics explores motion and forces.
• Kinematics describes motion, excluding causes.
• Dynamics describes motion, considering forces.
• Newton's laws form the bedrock of classical mechanics:
  • First law: Objects stay at rest or in motion unless a force acts.
  • Second law: Force = mass x acceleration (F = ma).
  • Third law: Every action has an equal, opposite reaction.
• Fundamental conservation laws exist:
  • Energy conservation: Energy transforms but isn't created/destroyed.
  • Momentum conservation: Total momentum in a closed system is constant.
  • Angular momentum conservation: Total angular momentum in a closed system is constant.

Thermodynamics

• Thermodynamics studies heat, work, and energy transfer.
• Core concepts:
  • Temperature: Average kinetic energy of particles in a system.
  • Heat: Energy transfer due to temperature differences.
  • Work: Energy transferred by force causing displacement.
• Laws of thermodynamics:
  • Zeroth law: Systems in equilibrium with a third system are in equilibrium with each other.
  • First law: Change in internal energy = heat added - work done.
  • Second law: Entropy in isolated systems increases or stays constant.
  • Third law: Entropy approaches a constant as temperature nears absolute zero.

Electromagnetism

• Electromagnetism studies interactions of electric charges and magnetic fields.
• Key concepts:
  • Electric charge: Matter property causing force in electromagnetic fields.
  • Electric field: Region around electric charges exerting force.
  • Magnetic field: Region around magnets or moving charges exerting magnetic force.
  • Electromagnetic waves: Oscillating electric/magnetic fields propagating in space, like light and X-rays.
• Maxwell's equations describe electric and magnetic field behavior:
  • Gauss's law (electricity): Relates electric field to charge.
  • Gauss's law (magnetism): No magnetic monopoles exist.
  • Faraday's law: Changing magnetic fields create electric fields.
  • Ampère-Maxwell's law: Magnetic field relates to electric current and changing electric fields.

Optics

• Optics is the study of light and its behavior.
• Key concepts:
  • Reflection: Light bouncing off surfaces.
  • Refraction: Light bending when passing between mediums.
  • Diffraction: Light waves spreading through openings or around obstacles.
  • Interference: Superposition of light waves creating patterns.
• Optical instruments:
  • Lenses: Focus or diverge light.
  • Mirrors: Reflect light.
  • Telescopes: Observe distant objects.
  • Microscopes: Observe small objects.

Quantum Mechanics

• Quantum mechanics explores matter/energy behavior at atomic/subatomic levels.
• Key concepts:
  • Quantization: Energy and momentum exist in discrete values.
  • Wave-particle duality: Particles act like waves; waves act like particles.
  • Uncertainty principle: Limits precision of knowing certain property pairs.
  • Superposition: Quantum systems exist in multiple states until measured.
  • Entanglement: Linked quantum systems share the same fate regardless of distance.

Relativity

• Relativity includes Einstein's special and general relativity.
• Special relativity covers space-time relationships:
  • Physics laws are constant for uniformly moving observers.
  • Light speed in a vacuum is constant for all observers.
  • Consequences include time dilation, length contraction, and mass increase.
• General relativity describes gravity as spacetime curvature from mass/energy:
  • Objects follow curved paths perceived as gravity.
  • Predicts gravitational lensing and waves.

Nuclear Physics

• Nuclear physics studies atomic nuclei's structure, properties, and reactions.
• Key concepts:
  • Nucleons: Protons and neutrons in the nucleus.
  • Isotopes: Atoms with the same number of protons but different numbers of neutrons.
  • Nuclear forces: Strong forces holding nuclei together.
  • Radioactivity: Unstable nuclei emitting particles/energy.
  • Nuclear reactions: Reactions involving nuclei, like fission and fusion.

Branches of Physics

• Classical Mechanics: Motion, forces, and energy at macroscopic scales.
• Electromagnetism: Electric/magnetic fields and interactions with matter.
• Thermodynamics: Heat, work, and energy transfer.
• Optics: Light and its behavior.
• Acoustics: Sound and its behavior.
• Quantum Mechanics: Matter/energy at atomic/subatomic levels.
• Nuclear Physics: Structure, properties, and reactions of atomic nuclei.
• Particle Physics: Basic matter constituents and their interactions.
• Condensed Matter Physics: Physical properties of matter in solid/liquid phases.
• Astrophysics: Physics of the universe, including stars, galaxies, and cosmology.