Vijay Shankar Sharma
Textbook physics terms. Not a BFUT reinterpretation. 371 terms. Textbook meanings only.
24 terms. Page 1 of 1.
astro · intro
A measure of the intrinsic brightness of a celestial object, defined as the apparent magnitude it would have if placed at a standard distance of 10 parsecs from the observer, removing the effect of actual distance. Because it reflects true luminosity rather than observed brightness, absolute magnitude allows astronomers to directly compare the brightness of stars located at very different distances from Earth.
thermo · intro
Also called: 0 kelvin
The lowest possible temperature, defined as 0 kelvin or -273.15 degrees Celsius. At this point a system has the minimum thermal energy allowed by quantum mechanics, since some zero-point motion always remains. No physical process has ever reached it exactly, though laboratories have cooled small samples to within a billionth of a degree using laser and magnetic trapping techniques. It serves as the reference point for the Kelvin temperature scale.
mechanics · intro
The rate at which an object's velocity changes over time, measured in meters per second squared. It is a vector, so it captures both speeding up, slowing down, and changing direction. A falling object near Earth's surface accelerates at roughly 9.8 meters per second squared due to gravity. Newton's second law ties acceleration directly to the net force acting on an object and its mass.
cosmology · intermediate
Also called: acoustic peaks
A series of characteristic bumps visible in the power spectrum of temperature fluctuations across the cosmic microwave background, produced by sound waves that propagated through the hot, dense plasma of the early universe before neutral atoms formed. The precise pattern, spacing, and relative heights of these acoustic peaks encode detailed information about the universe's geometry, composition, and the relative amounts of ordinary matter, dark matter, and dark energy.
mechanics · intermediate
Also called: least action
A quantity that combines a system's energy and time, or momentum and position, into a single number with units of energy multiplied by time. The principle of least action states that a physical system evolves along the path that makes this quantity stationary, usually a minimum. This idea underlies Lagrangian mechanics and extends into quantum theory, where the smallest meaningful unit of action is set by Planck's constant.
thermo · intermediate
A thermodynamic process in which a system exchanges no heat with its surroundings, so any change in internal energy comes entirely from work done on or by the system. Compressing gas quickly in an insulated cylinder is a common example, since there is no time for heat to escape. Adiabatic processes appear throughout thermodynamics, from engine cycles to the cooling of rising air parcels in the atmosphere.
nuclear · intro
A type of radioactive decay in which an unstable atomic nucleus emits an alpha particle, made of two protons and two neutrons bound together and identical to a helium-4 nucleus. This reduces the parent nucleus's atomic number by two and its mass number by four. Alpha decay is common in heavy elements like uranium and radium, and the emitted particles are stopped easily by a sheet of paper or a few centimeters of air.
nuclear · intro
Also called: helium nucleus
A particle made of two protons and two neutrons bound together, identical in structure to the nucleus of a helium-4 atom. Alpha particles carry a positive charge of plus two and are relatively heavy and slow compared to other radiation types, which makes them easy to stop with a sheet of paper. They are commonly emitted during the radioactive decay of heavy elements such as uranium.
em · intro
Also called: amp
The SI base unit of electric current, defined by fixing the numerical value of the elementary charge. One ampere corresponds to a flow of about 6.24 times ten to the eighteenth electrons per second past a given point in a conductor. It is named after French physicist Andre-Marie Ampere, an early investigator of the relationship between electricity and magnetism.
waves · intro
The maximum displacement or intensity of a wave or oscillation, measured from its equilibrium or rest position. For a sound wave, larger amplitude corresponds to louder sound; for a light wave, it relates to brightness. Amplitude is distinct from frequency, which describes how often the oscillation repeats. In simple harmonic motion, amplitude stays constant unless energy is added or removed from the system.
mechanics · intermediate
A measure of an object's rotational motion, calculated from its moment of inertia and angular velocity for a rotating body, or from its mass, velocity, and distance from a chosen point for an orbiting one. Angular momentum is conserved in any system with no external torque, which is why a spinning figure skater speeds up when pulling in their arms. It plays a central role in orbital mechanics and atomic structure.
mechanics · intro
The rate at which an object rotates or revolves around an axis, expressed in radians per second. It describes how quickly the angle of rotation changes with time, independent of the object's size. A point farther from the rotation axis moves faster in a straight-line sense but has the same angular velocity as a point closer in, since both sweep through the same angle in the same time.
particle · intermediate
The process in which a particle and its corresponding antiparticle meet and convert entirely into energy, typically in the form of photons, according to Einstein's mass-energy relation. For example, an electron and a positron annihilate to produce two gamma-ray photons. Annihilation is the reverse of pair production, in which energy converts into a particle-antiparticle pair, and both processes conserve total energy, momentum, and charge.
particle · intro
Matter composed of antiparticles, which have the same mass as their ordinary-matter counterparts but opposite electric charge and other quantum properties. The positron, for instance, is the antimatter counterpart of the electron. When matter and antimatter meet, they annihilate each other and release energy. Antimatter is rare in the observable universe, and explaining this imbalance between matter and antimatter is an open problem in particle physics and cosmology.
particle · intro
A particle that has the same mass as its ordinary counterpart but opposite values for properties like electric charge. Every known particle has a corresponding antiparticle; the electron's antiparticle is the positron, and the proton's is the antiproton. Some particles, like the photon, are their own antiparticle. When a particle meets its antiparticle, the pair typically annihilates into energy.
optics · intro
The opening in an optical system, such as a camera lens or telescope, through which light passes. A larger aperture lets in more light and improves resolution but reduces depth of field in imaging systems. Aperture size is often expressed as an f-number, the ratio of focal length to aperture diameter, and it directly affects both the brightness and sharpness of the resulting image.
astro · intro
A measure of how bright a celestial object appears from Earth, on a logarithmic scale where lower and negative numbers indicate brighter objects. It depends on both the object's true luminosity and its distance, so a nearby faint star can appear brighter than a distant powerful one. Apparent magnitude is distinguished from absolute magnitude, which measures intrinsic brightness at a standard reference distance.
mechanics · intro
The principle stating that an object submerged, wholly or partly, in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces. This explains why objects denser than water sink while less dense ones float, and why a ship made of steel can float if its overall shape displaces enough water. It was first described by the ancient Greek mathematician Archimedes.
astro · intermediate
A narrow, high-speed beam of ionized matter ejected from the vicinity of a compact object, such as a black hole, neutron star, or young star, typically launched along the object's rotation axis. Jets from supermassive black holes at the centers of active galaxies can extend for millions of light-years and are powered by the intense gravitational and magnetic energy near the central object. Their exact launching mechanism remains an active area of astrophysical research.
nuclear · intro
The basic building block of ordinary matter, consisting of a dense central nucleus made of protons and neutrons, surrounded by a cloud of electrons held in place by electromagnetic attraction. The number of protons defines which chemical element an atom belongs to. Atoms are extremely small, roughly a tenth of a nanometer across, yet almost all of their mass is concentrated in the nucleus.
nuclear · intro
The total mass of an atom, expressed in atomic mass units, where one unit is defined as one-twelfth the mass of a carbon-12 atom. It is determined mainly by the combined number of protons and neutrons in the nucleus, since electrons contribute very little mass. The atomic mass listed on a periodic table is usually a weighted average across an element's naturally occurring isotopes.
nuclear · intro
The number of protons in an atom's nucleus, which determines which chemical element the atom is. It is denoted by the symbol Z and defines an element's position on the periodic table. Atoms of the same element always share the same atomic number, even though they can have different numbers of neutrons, a variation known as isotopes.
waves · intermediate
The gradual loss of intensity of a wave, signal, or beam of particles as it travels through a medium, caused by absorption, scattering, or spreading. Light attenuates as it passes through fog or water, and radio signals attenuate with distance and obstacles. Attenuation is often described by an exponential decay law and is a key factor in designing communication systems and radiation shielding.
thermo · intro
Also called: Avogadro's number
The number of elementary units, such as atoms or molecules, in one mole of a substance, approximately 6.022 times ten to the twenty-third per mole. It links the microscopic scale of individual atoms to the macroscopic scale of measurable quantities like grams and liters. The constant is named after Italian scientist Amedeo Avogadro, though he did not calculate its exact value himself.