All Words Glossary

Glossary of Physics Terms
beginning with letter B
Browse the Physics Glossary

background Tweet Definition of background Like Definition of background on Facebook
  1. One's social heritage; what one did in the past/previously.
The lawyer had a in computer science.
  1. A part of the picture that depicts scenery to the rear or behind the main subject. Context.
  2. Information relevant to the current situation about past events; history.
  3. A less important feature of scenery (as opposed to foreground.)
There was tons of noise in the .
The photographer let us pick a for the portrait.
  1. (computing): (Windows): The solid color that provides contrast with items (usually icons) appearing on it.
  2. (computing): Activity on a computer that is not normally visible to the user
The antivirus program is running in the .
backscatter Tweet Definition of backscatter Like Definition of backscatter on Facebook
  1. The deflection of particles and/or radiation by nuclear and/or electromagnetic forces through angles greater than 90 degrees to the original direction of travel.
  2. The particles and/or radiation deflected in this manner.
  3. (military) A portion of the energy or a laser that is scattered back in the seeker's direction by an obscurant.
  1. To scatter particles and/or radiation by the atoms of the medium being passed through.
band Tweet Definition of band Like Definition of band on Facebook
  1. A strip of material wrapped around things to hold them together.
  2. A strip along the spine of a book where the pages are attached.
  3. A group of musicians, especially (a) wind and percussion players, or (b) rock musicians.
  4. A type of orchestra originally playing janissary music; i.e. marching band.
  5. A group of people loosely united for a common purpose (a band of thieves).
  6. (physics) A part of radio spectrum.
  7. (physics) A group of energy levels in a solid state material. Valence band, conduction band.
  8. (Canadian English) A group of aboriginals that has official recognition as an organized unit by the federal government of Canada.
  1. (intransitive) To group together for a common purpose.
  2. To fasten together with a band.
  3. (ornithology) To fasten an identifying band around (a bird's) leg.
bar Tweet Definition of bar Like Definition of bar on Facebook
  1. A solid, more or less rigid object with a uniform cross-section smaller than its length.
  2. (metallurgy) a solid metal object with uniform (round, square, hexagonal, octagonal or rectangular) cross-section, whose smallest dimension is .25 inch or greater (US), a piece of thinner material being called a strip.
Ancient Sparta used iron s instead of handy coins in more valuable alloi, to physically disencourage the use of money
  1. A cuboid piece of any solid commodity.
bar of chocolate
bar of soap
  1. A long, narrow drawn or printed rectangle, cuboid or cylinder, especially as used in a bar code or a bar chart.
  2. A business licensed to sell intoxicating beverages for consumption on the premises, or the premises themselves; public house.
  3. The counter of such a premises
  4. A similar device or simply a closet containing alcoholic beverages in a private house or a hotel room.
  5. An official order or pronouncement that prohibits some activity.
  6. (computing, whimsical, derived from fubar) Used to stand for some unspecified entity, usually a second entity following foo.
Suppose we have two objects, foo and bar
  1. (legal: the Bar) Short for the Bar Exam, the legal licensing exam.
He's studying hard to pass the Bar this time; he's failed it twice before.
  1. (British: the Bar) A collective term for barristers.
  2. (British: the Bar) (loosely) The profession of barristers.
  3. (music) A vertical line across a musical staff dividing written music into sections, typically of equal durational value.
  4. (music) One of these musical sections.
  5. (soccer) The crossbar
  6. An addition to a military medal, on account of a subsequent act
  7. A linear shoaling landform feature within a body of water.
  8. (nautical) A ridge or succession of ridges of sand or other substance, especially a formation extending across the mouth of a river or harbor or off a beach, and which may obstruct navigation. (FM 55-501).
  9. (heraldry) One of the ordinary, ordinaries in heraldry.
See wikipedia article on the topic: (w, Ordinary (heraldry))
verb (bars, barring, barred, barred)
  1. (transitive) To obstruct the passage of (someone or something).
  2. (transitive) To prohibit.
I couldn't get into the nightclub because I had been barred
  1. (transitive) To lock or bolt with a bar.
bar the door
barn Tweet Definition of barn Like Definition of barn on Facebook
noun (wikipedia, barn, barn (farm))
  1. A building, often found on a farm, used for storage or keeping animals such as cattle.
  2. (context, nuclear physics) A unit of surface area equal to 10-28 square metres.
  3. (rfv-sense) (slang) Short for barnacle, A barn is a person who latches on to another person (called the hull) and thinks he or she is somehow better because of his or her association with the hull.
baryon Tweet Definition of baryon Like Definition of baryon on Facebook
  1. (particles) A heavy subatomic particle created by the binding of quarks by gluons. Baryons have half-odd integral spin and are thus fermions. This category includes the common proton and neutron of the atomic nucleus.
base unit Tweet Definition of base unit Like Definition of base unit on Facebook
  1. A unit of measurement on which others are based.
The SI unit of velocity is metres per second, derived from the base units of time and distance.
  1. The main unit of a computer or hi-fi system.
When upgrading her computer she bought a new but kept the screen, keyboard and mouse.
beat Tweet Definition of beat Like Definition of beat on Facebook
  1. A pulsation or throb.
  2. A pulse on the beat level, the metric level at which pulses are heard as the basic unit. Thus a beat is the basic time unit of a piece.
  3. A rhythm.
  4. A pause with the camera focused on one shot, often a characters face (often used in screenplays/teleplays).
  5. The route of a patrol by a guard or officer as in walk the beat.
  6. In newspapering, the primary focus of a reporter's stories (such as police/courts, education, city government, business, etc.).
  7. A small part of a dramatic play.
verb (beats, beating, beat, beaten)
  1. To hit; to knock; to pound; to strike.
As soon as she heard the news, she went into a rage and the wall with her fists until her knuckles bled.
  1. To strike or pound repeatedly, usually in some sort of rhythm.
He danced hypnotically while she the atabaque.
  1. To win against; to defeat; to do better than, outdo, or excel someone in a particular, competitive event.
Jessica had little trouble beating John in tennis. He lost five games in a row.
No matter how quickly Joe finished his test, Roger always him.
  1. (context, intransitive, nautical) To sail to windward using a series of alternate tacks across the wind.
  2. To mix food in a rapid fashion. cf. whip.
Beat the eggs and whip the cream.
  1. (gay slang) fabulous
Her makeup was beat!
  1. exhausted
After the long day, she was feeling completely .
beauty quark Tweet Definition of beauty quark Like Definition of beauty quark on Facebook
  1. (particles) original name for the bottom quark
bel Tweet Definition of bel Like Definition of bel on Facebook
  1. A measure of sound intensity that is 10 decibels, and is defined as B = log10(P 1/P 2), where P1 and P2 are the relative powers of the sound.
beta particle Tweet Definition of beta particle Like Definition of beta particle on Facebook
  1. (particles) An energetic electron or positron produced as the result of a nuclear reaction or nuclear decay.
betatron Tweet Definition of betatron Like Definition of betatron on Facebook
  1. (physics) a form of cyclotron used to accelerate electrons to high speed
BeV Tweet Definition of BeV Like Definition of BeV on Facebook
  1. (physics) billion electron volt, 109 eV. A unit used for measuring the energy of subatomic particles.
binding energy Tweet Definition of binding energy Like Definition of binding energy on Facebook
  1. (physics) the energy needed to separate the constituent parts of an atom or nucleus; equivalent to the mass defect
black Tweet Definition of black Like Definition of black on Facebook
  1. (colour) The colour/color perceived in the absence of light.
<table><tr><td height="25">black colour: &nbsp;</td><td bgcolor="black" width="80">&nbsp; </td></tr></table>
  1. A black dye, pigment.
  2. A pen, pencil, crayon, etc., made of black pigment.
  3. (context, sometimes capitalised) A person of African descent.
  4. (context, billiards, snooker, pool) the black: The black ball.
  5. (baseball) The edge of home plate
  1. To make black, to blacken.
  1. (context, of an object) absorbing all light and reflecting none; dark and colourless.
  2. (context, of a place, etc) without light.
  3. (context, sometimes capitalized) Relating to persons of African descent or (especially in the US) their culture.
  4. (context, Ireland, idiomatic) Overcrowded.
  5. Bad; evil.
    • 1655, Benjamin Needler, Expository notes, with practical observations; towards the opening of the five first chapters of the first book of Moses called Genesis. London: N. Webb and W. Grantham, page 168.
    • : ...what a day would that be, when the Ordinances of Jesus Christ should as it were be excommunicated, and cast out of the Church of Christ.
      1. Illegitimate, illegal or disgraced.
    • 1866, The Contemporary Review, London: A. Strahan, page 338.
    • :Foodstuffs were rationed and, as in other countries in a similar situation, the black market was flourishing.
blackbody Tweet Definition of blackbody Like Definition of blackbody on Facebook
  1. (physics) a theoretical body, approximated by a hole in a hollow black sphere, that absorbs all incident electromagnetic radiation and reflects none; it has a characteristic emission spectrum
blue Tweet Definition of blue Like Definition of blue on Facebook
noun (wikipedia, Blue, Blue (colour))
  1. (colorbox, blue) The colour of the clear sky or the deep sea, between green and violet in the visible spectrum, and one of the primary additive colours for transmitted light; the colour obtained by subtracting red and green from white light using magenta and cyan filters.
  2. (context, snooker) One of the colour balls used in snooker with a value of 5 points.
verb (blues, blueing or bluing, blued)
  1. (transitive) To make .
  2. (transitive) (context, Metallurgy) To treat the surface of steel so that it is passivated chemically and becomes more resistant to rust.
See Wikipedia article on bluing steel: (w, bluing (steel))
  1. (intransitive) To turn .
adjective (blu, er)
  1. Of the colour blue.
  2. (colloquial)(nautical) depressed, Depressed, melancholic, sad. The phrase "feeling blue" was coined from a custom among old deepwater ships to fly blue flags or have a blue band painted along the hull if the vessel lost a captain or officers during a voyage.
  3. (colloquial)(context, entertainment) pornographic, Pornographic.
  4. (US, politics) Of states or other political entities, tending to vote for the Democratic Party.
Many of the traditionally states are on the east and west coasts.
Congress turned in the mid-term elections.
  1. (rfv-sense) (US, politics) Of or pertaining to the Democratic Party.
a advertisement
  1. (astronomy) of the higher-frequency region of the part of the electromagnetic spectrum which is relevant in the specific observation.
body Tweet Definition of body Like Definition of body on Facebook
noun (bodies)
  1. The physical structure of a human or animal seen as one single organism.
I saw them walking from a distance, their bodies strangely angular in the dawn light.
  1. The fleshly or corporeal nature of a human, as opposed to the spirit or soul.
The is driven by desires, but the soul is at peace.
  1. A corpse.
Her was found at four o'clock, just two hours after the murder.
  1. The torso, the main structure of a human or animal frame excluding the extremity, extremities (limbs, head, tail).
The boxer took a blow to the .
  1. The largest or most important part of anything, as distinct from its appendages or accessory, accessories.
The bumpers and front tyres were ruined, but the of the car was in remarkable shape.
  1. (archaic) The section of a dress extending from the neck to the waist, excluding the arms.
Penny was in the scullery, pressing the of her new dress.
  1. An organisation, company or other authoritative group.
The local train operating company is the managing for this section of track.
  1. A group of men or people having a common purpose or opinion; a mass.
I was escorted from the building by a of armed security guards.
  1. A unified collection of details, knowledge or information.
We have now amassed a of evidence which points to one conclusion.
  1. Any physical object or material thing.
All bodies are held together by internal forces.
  1. Substance; physical presence.
We have given to what was just a vague idea.
  1. Comparative viscosity, solidity or substance (in wine, colours etc.).
The rioja, sadly, lacked .
  1. (programming) The code of a subroutine, contrasted to its signature and parameters.W:Subroutine, W
boil Tweet Definition of boil Like Definition of boil on Facebook
  1. A localized accumulation of pus in the skin, resulting from infection.
  2. The point at which fluid begins to change to a vapour.
Add the noodles when the water comes to the .
  1. The collective noun for a group of hawks.
bolometer Tweet Definition of bolometer Like Definition of bolometer on Facebook
  1. (physics) A sensitive device for detecting and measuring the energy of electromagnetic radiation
bombard Tweet Definition of bombard Like Definition of bombard on Facebook
  1. a medieval form of cannon, used chiefly in sieges for throwing heavy stone balls.
  1. To attack something with bombs, artillery shells, or other missiles.
  2. (figuratively) To attack something or someone by directing objects at them.
  3. (physics) to direct an intense stream of high-energy particles, usually sub-atomic or made of at most a few atoms, at a substance.
boson Tweet Definition of boson Like Definition of boson on Facebook
  1. (particles) A particle with totally symmetric composite quantum states, which exempts them from the Pauli exclusion principle, and that obey Bose-Einstein statistics. They have integer spin. Among them are many elementary particles, and some (gauge bosons) are known to carry the fundamental forces. Compare fermion.
bottom quark Tweet Definition of bottom quark Like Definition of bottom quark on Facebook
  1. (particles) A quark having a fractional electric charge of -1/3 and a mass about 4,100 to 4,400 MeV?. Symbol: b
Bragg's law Tweet Definition of Bragg Like Definition of Bragg
  1. (physics) equates the angle <math>(\theta)</math> between the incident and scattered ray to the spacing <math>(d)</math> between the crystal planes and the wavelength <math>(\lambda)</math> of the radiation - <math>n\lambda=2d\sin(\theta) \,</math>
bremsstrahlung Tweet Definition of bremsstrahlung Like Definition of bremsstrahlung on Facebook
  1. the electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when it is deflected by another charged particle, such as an atomic nucleus
British thermal unit Tweet Definition of British thermal unit Like Definition of British thermal unit on Facebook
noun (or BTU or Btu)
  1. The quantity of heat required to raise the temperature of one pound of water one degree Fahrenheit at a particular temperature (there are several different precise definitions) and a pressure of one atmosphere. Symbol BTU or Btu.
Brown Tweet Definition of Brown Like Definition of Brown on Facebook
proper noun
  1. An English, Irish and Scottish surname.
  2. A nickname for someone with brown hair or a dark complexion.
Brownian movement Tweet Definition of Brownian movement Like Definition of Brownian movement on Facebook
  1. random, Random motion of particles suspended in a fluid, arising from those particles being struck by individual molecules of the fluid.
bubble Tweet Definition of bubble Like Definition of bubble on Facebook
  1. A spherically contained volume of air, especially one made from soapy liquid.
  2. A small spherical cavity in a solid material.
  3. Anything resembling a hollow sphere.
  4. A period of intense speculation in a market, causing prices to rise quickly to irrational levels as the metaphorical bubble expands, and then fall even more quickly as the bubble bursts.
verb (bubbl, es)
  1. (intransitive) To produce bubbles, to rise up in bubbles (such in foods cooking).
  2. (context, transitive, archaic) To cheat, delude.
  3. (context, intransitive, Scotland, Northern England) To cry, weep.
buoyancy Tweet Definition of buoyancy Like Definition of buoyancy on Facebook
  1. (physics) the upward force on a body immersed or partly immersed in a fluid
  2. (context, by extension) resilience or cheerfulness

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