Physics: Core Concepts

• Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force.
• Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves.

Core Concepts

• Classical mechanics deals with the motion of macroscopic objects.
• It is based on Newton's laws of motion.
• Concepts include displacement, velocity, acceleration, force, mass, momentum, energy, and work.
• Thermodynamics is the study of energy transfer and transformations in physical systems.
• Key concepts include temperature, heat, entropy, and the laws of thermodynamics.
• Electromagnetism describes the interactions of electric charges and magnetic moments.
• It is governed by Maxwell's equations.
• Key concepts include electric charge, electric field, magnetic field, electric current, and electromagnetic waves.
• Optics studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.
• Key concepts include reflection, refraction, diffraction, interference, and polarization.
• Quantum mechanics deals with the behavior of matter and energy at the atomic and subatomic levels.
• It introduces concepts such as wave-particle duality, superposition, and quantum entanglement.
• Relativity:
• Special relativity deals with the relationship between space and time.
• It postulates that the speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
• General relativity is a theory of gravitation.
• It describes gravity as a curvature of spacetime caused by mass and energy.

Mechanics

• Kinematics describes the motion of objects without considering the forces that cause the motion.
• Key concepts include displacement, velocity, acceleration, and time.
• Equations of motion relate these quantities for objects moving with constant acceleration.
• Dynamics studies the forces that cause motion.
• Newton's laws of motion relate force, mass, and acceleration.
• Key concepts include force, mass, weight, momentum, impulse, and energy.
• Work and energy are fundamental concepts in mechanics.
• Work is the transfer of energy when a force causes displacement.
• Energy can exist in various forms, including kinetic energy, potential energy, and thermal energy.
• Conservation laws are fundamental principles in physics.
• The law of conservation of energy states that energy cannot be created or destroyed but can be transformed from one form to another.
• The law of conservation of momentum states that the total momentum of an isolated system remains constant.

Thermodynamics

• The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.
• This law establishes the concept of temperature.
• The first law of thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system.
• This law is a statement of the conservation of energy.
• The second law of thermodynamics states that the entropy of an isolated system tends to increase over time.
• This law implies that heat cannot spontaneously flow from a cold body to a hot body.
• The third law of thermodynamics states that the entropy of a system approaches a constant value as the temperature approaches absolute zero.
• This law implies that it is impossible to reach absolute zero in a finite number of steps.
• Heat transfer can occur through conduction, convection, and radiation
• Conduction is the transfer of heat through a material due to a temperature difference.
• Convection is the transfer of heat by the movement of a fluid.
• Radiation is the transfer of heat by electromagnetic waves.

Electromagnetism

• Electric charge is a fundamental property of matter.
• There are two types of electric charge: positive and negative.
• Like charges repel each other, and opposite charges attract each other.
• Coulomb's law describes the force between two electric charges.
• The force is proportional to the product of the charges and inversely proportional to the square of the distance between them.
• Electric field is the force per unit charge exerted on a test charge.
• It is a vector quantity.
• Electric field lines represent the direction and strength of the electric field.
• Electric potential is the potential energy per unit charge.
• It is a scalar quantity.
• Voltage is the difference in electric potential between two points.
• Electric current is the rate of flow of electric charge.
• It is measured in amperes (A).
• Ohm's law relates voltage, current, and resistance.
• Magnetism
• Magnetic fields are produced by moving electric charges.
• Magnetic field lines represent the direction and strength of the magnetic field.
• Electromagnets are created by running current through a coil of wire.
• Maxwell's equations are a set of four equations that describe the behavior of electric and magnetic fields.
• These equations unify electricity and magnetism.
• Electromagnetic waves are disturbances that propagate through space, carrying energy.
• Examples include radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

Optics

• Reflection is the bouncing of light off a surface.
• The angle of incidence is equal to the angle of reflection.
• Refraction is the bending of light as it passes from one medium to another.
• The amount of bending depends on the refractive indices of the two media.
• Lenses are used to focus or diverge light.
• Convex lenses converge light, while concave lenses diverge light.
• Interference occurs when two or more waves overlap.
• Constructive interference occurs when the waves are in phase, resulting in a larger amplitude.
• Destructive interference occurs when the waves are out of phase, resulting in a smaller amplitude.
• Diffraction is the spreading of waves as they pass through an aperture or around an obstacle.
• Polarization is the orientation of the electric field vector of a light wave.

Quantum Mechanics

• Quantum mechanics postulates that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values (quantization).
• Wave-particle duality:
• Particles, such as electrons and photons, exhibit both wave-like and particle-like properties.
• The de Broglie wavelength relates the wavelength of a particle to its momentum.
• Heisenberg's uncertainty principle states that it is impossible to know both the position and momentum of a particle with perfect accuracy.
• Quantum entanglement:
• Two or more particles can become linked together in such a way that they share the same fate, no matter how far apart they are.
• Quantum field theory combines quantum mechanics with special relativity.
• It describes particles as excitations of quantum fields.

Relativity

• Special relativity is based on two postulates:
• The laws of physics are the same for all observers in uniform motion.
• The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source.
• Time dilation is the phenomenon that time passes slower for an observer who is moving relative to another observer.
• Length contraction is the phenomenon that the length of an object appears to be shorter to an observer who is moving relative to the object.
• General relativity is based on the principle of equivalence.
• Gravitational mass and inertial mass are equivalent.
• Gravity is the curvature of spacetime caused by mass and energy.
• Black holes are regions of spacetime where gravity is so strong that nothing, not even light, can escape.
• Gravitational waves are ripples in spacetime caused by accelerating masses.

Overview of physics as a natural science studying matter, motion, energy, and force. Covers classical mechanics based on Newton's laws, thermodynamics focusing on energy transfer, and electromagnetism governed by Maxwell's equations.