Glossary of physics

Glossary of Physics

This glossary of physics is a comprehensive list of terms, concepts, and definitions that are fundamental to the field of physics. It serves as a reference for students, educators, and anyone interested in understanding the principles that govern the physical universe.

A

Acceleration

Acceleration is the rate of change of velocity of an object with respect to time. It is a vector quantity, having both magnitude and direction. The SI unit of acceleration is meters per second squared (m/s²).

Amplitude

Amplitude is the maximum extent of a vibration or oscillation, measured from the position of equilibrium. It is often used in the context of waves, such as sound waves or electromagnetic waves.

B

Black Hole

A black hole is a region of spacetime where gravity is so strong that nothing, not even light, can escape from it. The boundary of a black hole is called the event horizon.

Buoyancy

Buoyancy is the force exerted on an object that is wholly or partly immersed in a fluid. It is the reason why objects float or sink in water.

C

Capacitance

Capacitance is the ability of a system to store an electric charge. It is measured in farads (F) and is defined as the charge stored per unit voltage.

Conservation Laws

Conservation laws are fundamental principles in physics that state certain properties of isolated physical systems do not change over time. Examples include the conservation of energy, momentum, and charge.

D

Diffraction

Diffraction is the bending of waves around obstacles and the spreading out of waves past small openings. It is a phenomenon that occurs with all types of waves, including sound waves and light waves.

Doppler Effect

The Doppler effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. It is commonly observed in sound waves and electromagnetic waves.

E

Entropy

Entropy is a measure of the amount of disorder or randomness in a system. In thermodynamics, it is a central concept that quantifies the irreversibility of natural processes.

Electromagnetic Spectrum

The electromagnetic spectrum is the range of all types of electromagnetic radiation, from radio waves to gamma rays. It includes visible light, which is the portion of the spectrum that can be detected by the human eye.

F

Force

Force is an interaction that, when unopposed, will change the motion of an object. It is a vector quantity, having both magnitude and direction, and is measured in newtons (N).

Frequency

Frequency is the number of occurrences of a repeating event per unit of time. It is measured in hertz (Hz) and is commonly used to describe waves, such as sound waves and electromagnetic waves.

G

Gravity

Gravity is a natural phenomenon by which all things with mass or energy are brought toward one another. It is the force that gives weight to physical objects and causes them to fall toward the Earth when dropped.

Gravitational Waves

Gravitational waves are ripples in spacetime caused by some of the most violent and energetic processes in the universe, such as colliding black holes or neutron stars.

H

Heisenberg Uncertainty Principle

The Heisenberg uncertainty principle is a fundamental theory in quantum mechanics that states it is impossible to simultaneously know the exact position and momentum of a particle.

Holography

Holography is a technique that enables a light field to be recorded and later reconstructed to create a three-dimensional image of an object.

I

Inertia

Inertia is the resistance of any physical object to any change in its velocity. This includes changes to the object's speed or direction of motion.

Interference

Interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude.

J

Joule

The joule is the SI unit of energy, equivalent to the energy transferred when a force of one newton acts on an object in the direction of the force's motion through a distance of one meter.

K

Kinetic Energy

Kinetic energy is the energy that an object possesses due to its motion. It is defined as one half of the mass of the object multiplied by the square of its velocity.

Kelvin

The kelvin is the base unit of temperature in the International System of Units (SI), and is one of the seven SI base units.

L

Light

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the portion of the spectrum that can be seen by the human eye.

Lagrangian

The Lagrangian is a function that summarizes the dynamics of a system. It is used in the formulation of the principle of least action in classical mechanics.

M

Mass

Mass is a measure of the amount of matter in an object. It is typically measured in kilograms (kg) and is a fundamental property of physical objects.

Momentum

Momentum is the product of the mass and velocity of an object. It is a vector quantity and is conserved in isolated systems.

N

Neutron

A neutron is a subatomic particle found in the nucleus of an atom. It has no electric charge and a mass slightly greater than that of a proton.

Newton's Laws of Motion

Newton's laws of motion are three physical laws that together laid the foundation for classical mechanics. They describe the relationship between the motion of an object and the forces acting on it.

O

Ohm's Law

Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. It is usually expressed as V = IR, where V is the voltage, I is the current, and R is the resistance.

Optics

Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.

P

Photon

A photon is a quantum of electromagnetic radiation. It is the basic unit that makes up all light and is a fundamental particle in quantum mechanics.

Potential Energy

Potential energy is the energy held by an object because of its position relative to other objects, stresses within itself, its electric charge, or other factors.

Q

Quantum Mechanics

Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles.

Quark

A quark is a type of elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons.

R

Relativity

Relativity is a theory developed by Albert Einstein that describes the laws of physics in the presence of gravitational fields. It includes both the special theory of relativity and the general theory of relativity.

Refraction

Refraction is the change in direction of a wave passing from one medium to another caused by its change in speed.

S

Superconductivity

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.

String Theory

String theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings.

T

Thermodynamics

Thermodynamics is the branch of physics that deals with the relationships between heat and other forms of energy. It describes how thermal energy is converted to and from other forms of energy and how it affects matter.

Torque

Torque is a measure of the force that can cause an object to rotate about an axis. It is a vector quantity and is measured in newton-meters (Nm).

U

Uncertainty Principle

The uncertainty principle is a fundamental concept in quantum mechanics that states that certain pairs of physical properties, like position and momentum, cannot both be known to arbitrary precision.

Universe

The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.

V

Velocity

Velocity is the rate of change of the position of an object, a vector quantity that specifies both the speed and direction of the object's motion.

Voltage

Voltage is the difference in electric potential between two points. It is a measure of the potential energy per unit charge and is measured in volts (V).

W

Wave

A wave is a disturbance that transfers energy through matter or space, with little or no associated mass transport. Waves can be mechanical, electromagnetic, or matter waves.

Work

Work is the energy transferred to or from an object via the application of force along a displacement. It is a scalar quantity and is measured in joules (J).

X

X-ray

X-rays are a form of electromagnetic radiation with wavelengths shorter than ultraviolet light but longer than gamma rays. They are used in medical imaging and other applications.

Y

Young's Modulus

Young's modulus is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression. It is a mechanical property that measures the stiffness of a solid material.

Z

Zero Point Energy

Zero point energy is the lowest possible energy that a quantum mechanical physical system may have. Unlike in classical mechanics, quantum systems constantly fluctuate in their lowest energy state due to the Heisenberg uncertainty principle.