Bremsstrahlung: Acceleration / Deceleration?

[Rennhack]

In the process known as Bremsstrahlung, some books say that the electron accelerates, others say it decelerates.  Here is a breakdown, which should enlighten us all.

Either way:

Argon National Lab-7291 Radiation Safety Technician Training Course, better known as “Moe study guide.” By H.J. Moe

When a charged particle is either accelerated or decelerated in an electronic field, electromagnetic radiation may be given off.  If an electron passes close to an atom while traversing a substance, the charge Z on the nucleus will exert a force on the electron.  This will cause its path to be bent.  During this acceleration the electron may radiate energy of any amount from zero up to its total kinetic energy.

Health Physics, Principals of Radiation Protection. D.J. REES, M.I.T. Press, p. 23, 1967. 

Continuous x-rays, a.k.a. Bremsstrahlung, is due to the acceleration of free electrons or charged particles.  Produced by x-ray machines or by stopping of B-rays in an absorber.

Health Physics, Principals of Radiation Protection. D.J. REES, M.I.T. Press, p. 48, 1967. 

... The continuous spectrium is due to the rapid slowing down of electrons in the target due to interaction the atomic electric field.  This radiation is known as 'Bremsstrahlung'.  ...

Accelerated:

Atoms, Radiation and Radiation Protection by James E. Turner

A beta particle, having little mass, can be accelerated strongly by the electromagnetic force within an atom and thereby emit radiation, called Bremsstrahlung.  Bremsstrahlung occurs when a beta particle is deflected in the electric field of a nucleus.

Introduction to Health Physics by Herman Cember

Bremsstrahlung consists of X-rays emitted when high-speed charged particles suffer rapid acceleration.  When a beta particle passes close to a nucleus, the strong attractive coulomb force causes the beta particle to deviate sharply from its original path.  The change in direction is due to radical acceleration, and the beta particle, in accordance with classic theory, loses energy by electromagnetic radiation at a rate proportional to the square of the acceleration.

Decelerated:

Radiation Protection in Medical Rediography. Ststkiewicz-Sherer, Mosby, p. 374, 1993. 

Ionozing electromagnetic radiation that is nonuniform in energy and wavelength and that is produced when a bombarding beam of electrons in an x-ray tube undergoes deceleration by interaction with the nuclei of the x-ray tube target atoms.

Bjorken, J. D. and Drell, S. D. "Bremsstrahlung." §7.6 in Relativistic Quantum Mechanics. New York: McGraw-Hill, pp. 120-127, 1964. 

Electromagnetic radiation that occurs when charged particles with energies large compared to their rest energies are decelerated over a very short distance. Since electrons are much lighter than protons, electron bremsstrahlung is the most common. In bremsstrahlung, a continuous spectrum with a characteristic profile and energy cutoff (i.e., wavelength minimum) is produced. In addition, lines can appear super imposed, corresponding to the ejection of K and L shell electrons knocked out of atoms in collisions with the high-energy electrons.

The Health Physics Fundamentals Study Guide from Combustion Engineering, better known as the “North East Utilities Study Guide”

When a high energy beta particle passes close to a heavy nucleus it is deflected sharply by the strong electric field.  When the beta particle is deflected (and thus slowed down) it emits electromagnetic energy in the form of X-rays.

Handbook of Health Physics and Radiological Health, better known as the Rad Health Handbook.

Bremsstrahlung – Secondary electromagnetic radiation (x-rays) produced by the deceleration of charged particles through matter.

Fundamentals of Radiation Protection by H.F. Henry

Higher energy electrons also lose energy by their deceleration in the electric field of an atom, with the emission of electromagnetic waves.  Such radiation is called Bremsstrahlung.

Too vague:

US Department of Energy Radiological Control Technician Phase I Core Academic Training Study Guide., better known as the DOE Core study guide

A high energy beta penetrates the electron cloud surrounding the nucleus of the atom, and experiences the strong electrostatic force of the positively charged nucleus.  This results in a change in velocity and the emission of a Bremsstrahlung X-ray.

Basic Nuclear Physics, Bureau of Naval Personnel, NAVPERS 10786, 1958 pp. 112-113

When a high-energy beta particle passes close to a heavy nucleus, it is deflected sharply by the strong electric field.  In being deflected, a beta particle is found to emit energy in the form of an X-ray.  Radiation produced in this way is called bremsstrahlung, which is a german word meaning "breafing radiation".  This term arises because a beta is continually slowed down by successive bremsstrahlung processes.

The Final Word:

Radiation Protection by Jacob Shapiro

Bremsstrahlung production by acceleration of bombarding electrons.  Electrons accelerated (shown here as a change of direction) near the highly charged nucleus of a heavy element may lose all or most of their energy through the emission of photons (called Bremsstrahlung, meaning “breaking radiation”)

The most important mechanism, from the point of view of the use of x-rays in radiography, is through a violent acceleration of the electron, resulting in the sharp deflection, as it interacts with the electrical field around the nucleus.  Such acceleration results in the emission of photons of x-radiations. The photons are generally referred to as Bremsstrahlung (breaking radiation), because the electrons lose energy and slow down in the process of emitting the radiation.

NRRPT Prep Course 1st Edition 1991 RI-Tech Inc.

Bremsstrahlung is an interaction that produces x rays from the kinetic energy of charged particles.  It is predominantly a beta particle interaction.  It occurs when a charged particle undergoes a rapid acceleration.  (Remember that acceleration is a vector quantity and that it can be either positive or negative in value.)  When a beta comes in close proximity to an atom, it will be deflected, which is a negative acceleration.  The energy of the photon given off is equal to the loss in kinetic energy of the beta.

Basic Radiation Protection Technology 4th Edition 2000 by Daniel Gollnick

Bremsstrahlung is a word of German extraction which translates literally as “breaking radiation”, that is, radiation generated when the charged particle puts on the breaks.  The causative agent is again the Coulomb force which produces a deflection in the path of the charged particle.  This change in direction is, in the physics sense, a negative acceleration (a de-celeration if you prefer) because the velocity vector changes with the directional change and the speed of the particle is reduced due to the energy loss.  The radiation emitted by the particle, the Bremsstrahlung, is electromagnetic in nature.  

[Rennhack]

Sounds to me like the Coulumbic force accelerates the electron, causing the energy to be emitted, which then leaves with less kinetic energy, decelerated.

I think some of those books should be a little more complete in their explanation.  I remember the last NEU test I took in 2000 had a question about this, and "accelerate" was the answer. However, the NEU study guide never mentions 'accelerate', but does mention 'decelerate'.

The Health Physics Fundamentals Study Guide from Combustion Engineering, better known as the “North East Utilities Study Guide”

When a high energy beta particle passes close to a heavy nucleus it is deflected sharply by the strong electric field.  When the beta particle is deflected (and thus slowed down) it emits electromagnetic energy in the form of X-rays.

[alphadude]

 Electromagnetic radiation that occurs when charged particles with energies large compared to their rest energies are decelerated over a very short distance. Since electrons are much lighter than protons, electron bremsstrahlung is the most common. In bremsstrahlung, a continuous spectrum with a characteristic profile and energy cutoff (i.e., wavelength minimum) is produced.

the increase in energy (acceleration) dont make sense when energy is lost at the same time? (photons being produced)

remember how an xray machine works- the electrons are accelerated to increase their effect when they slam (brakes) into the target to produce those wonderful xrays.  xrays dont happen when the electrons are in flight or being speeded up-  energy should be conserved

[SloGlo]

"Radiation Protection by Jacob Shapiro
Quote:
Bremsstrahlung production by acceleration of bombarding electrons.  Electrons accelerated (shown here as a change of direction) near the highly charged nucleus of a heavy element may lose all or most of their energy through the emission of photons (called Bremsstrahlung, meaning “breaking radiation”)

The most important mechanism, from the point of view of the use of x-rays in radiography, is through a violent acceleration of the electron, resulting in the sharp deflection, as it interacts with the electrical field around the nucleus.  Such acceleration results in the emission of photons of x-radiations. The photons are generally referred to as Bremsstrahlung (breaking radiation), because the electrons lose energy and slow down in the process of emitting the radiation."  

interesting choice of quote, mike.  i was always under the impression that bremsstrahlung was "braking" radiation.  however, the "breaking" radiation terminology mr. shapiro uses would work for both acceleration and deceleration.  look at it as radition that is breaking off from the electron as it undergoes velocity changes.  hmmm  :-?
cool thread, nowz eye gotz sumtin ta think bout twoday.

[metalman40]

Acceleration is the rate at which the velocity vector changes   Acceleration = change in velocity/time it can be either negative or positive. Decelleration is an undefined term in physics. When the beta interacts with the high Z electron cloud it is accelerated by a negative or positive value.

[Rain Man]

See attached link on the mathematics of "coherent bremsstrahlung":


http://zeus.phys.uconn.edu/halld/cobrems-7-97/

[St Raphael]

Rain Man - great site.  Here are a few more  


www.slac.stanford.edu/grp/rd/epac/Meeting/200011/bosted1.pdf

http://personal.tcu.edu/~quarles/bremspec.htm

http://scienceworld.wolfram.com/physics/Bremsstrahlung.html

[CheeseheadNuke]

Metalman is correct. An object traveling at some velocity in a given direction is defined as acceleration in classical physics. Even if the velocity decreases, the electron accelerates due to the directional change. Deceleration is not a classical physics term.

[Rennhack]

When the beta interacts with the high Z electron cloud

I hate to be picky, no one likes to be corrected, but I dojn't want the juniors to read that and take it as gospel... It isn't an interaction with the electron cloud, it is with the coulomb force from the protons. (At least most of the time.)

[alphadude]

perhaps we are discussing the limitations of english language-deceleration is a common term in our language and is readily moving into the classical sciences- (why say negative acceleration when one word says it all-) the definitions should express it classically as negative acceleration.. maybe thats why its bremsstrahlung in lieu of negative acceleration energy quantum....

[RAD-GHOST]

  Hey, it's all in the wording!  Is that braking, as in slow down, or brake left/right?  Once again my allergies have increased due to the amount of dust I have to wipe from these antiques.  My opinion, for what it is worth, is that the person who wrote that NU test question, with the answer as Accelerating, is WRONG!  I believe that person compiled a number of events, beyond the Bremsstrahlung theory, to justify an ambiguous answer.  I guess it's just the nuclear mantality!  Bremsstrahlung, in German, translates to," Braking Radiation".  Therefore someone has to make a stand and say it doesn't!  

  As I was taught, Brensstrahlung Radiation is emited when a high energy electron is deflected off of its mean free path, due to the influence of a high mass nuclide.  At the time of this event, the electron does in fact decrease in its energy state, or in layman terms," Brakes "!  This can be measured by comparing the resulting electron energy and the secondary photon produced.  The Bremsstrahlung photon is produced at the time of the vector change, not after the vector change.  Based on this immediate radical change in electron direction and the secondary photon produced, it all falls under the conservation of mass/energy.  Mass is energy and energy is mass, they convert directly to each other.  

  However the electrons energy is influenced, after the change in direction, due to the influencing nuclide, seems unrelated to the actual Bremsstrahlung event, even if it happens simultaniously.

  I guess you'd just have to say, " It's one of those physics things"!

[Rain Man]

Rad-Ghost.  That may be very true.  The term "bremsstrahlung" may be one of those words in a foreign language that defies easy translation in to english.

[St Raphael]

According to Merriam-Webster OnLine

Main Entry: brems·strah·lung
Pronunciation: 'brem(p)-"shträ-l&[ng]
Function: noun
Etymology: German, literally, decelerated radiation
Date: 1939
: the electromagnetic radiation produced by the sudden retardation of a charged particle in an intense electric field (as of an atomic nucleus); also : the process that produces such radiation

Also, IN/US Systems, Inc. states;
"Bremsstrahlung - When ß-particles interact with their surroundings to give up their energy, one of three processes occur:

Elastic collisions. Appreciable amounts of energy are transferred to whole atoms and then largely dissipated as heat.

Inelastic collisions. Energy is transferred to the electronic structure of the surrounding medium and subsequent energy loss proceeds via processes involving the activated surroundings. Incidentally this is the first step of the scintillation process.

Radiative loss (Bremsstrahlung). Deceleration of the charged particle in the coulomb field of a nucleus gives rise to the emission of electromagnetic radiation.
Bremsstrahlung, from the German for retarded radiation, is a continuous spectrum largely of soft X-rays but extending into the visible. The precise distribution of the energy is a function of both the energy of the charged particles and the atomic number Z of the target atom."

[actinium224]

Let's not limit Bremsstrahlung to electrons.  Any charged particle can undergo Bremsstrahlung, but the probability of an occurrence is inversely proportional to the square of the mass of the charged particle.  This means that although protons can undergo the interaction, it is ~3 million times less likely to occur than for electrons/positrons.  With Bremmstrahlung only accounting for 2-3% of all coulombic interactions, this would truly put it into the hair-splitting category.  
As an aside, actually seeing the results of Bremmstrahlung was interesting.  Especially since it was from strontium contaminated dog effluent in a metal drum.  

[Already Gone]

Well, technically Metalman is right.  I used to have a Physics instructor who would fly into a fit if someone used the word "deceleration".  Since acceleration is defined as the rate of change of velocity, and velocity is a vector quantity (speed is one variable and direction is the other) whenever the velocity changes, you have acceleration.  For example, a yo-yo being spun in a circle at constant speed is constantly accelerating, or stepping on the brakes in a northboud car causes acceleration in the southbound direction even though the car continues to move northward.
The same instructor was adamant that there was no such thing as centrifugal force.  Technically, he was correct there also, but the concept of centrifugal force is a convenient way to describe the combination of the forces that are acting on a body.
Likewise, deceleration is a commonly accepted term for negative acceleration.  I guess the correct answer to the question is "BOTH".

[RAD-GHOST]

Again, It's all in the wording!  Accelerate or Decelerate, who cares.  How about just describing the concept of what happens in it's simplest form.  There are a lot of high tech terms available in this industry, the use of which, will impress your friends and neighbors.  But, these recently posted question, seem like a great tool for others who may have never seen the topics, or understood the concepts. It is also very interesting to see the input from the members.  Although it may be hard to any two of us to agree 100% on a simple solution , it's great to see the Effort, Energy, Research and Opinions on these topics.

[Rain Man]

Again, It's all in the wording!  Accelerate or Decelerate, who cares.  How about just describing the concept of what happens in it's simplest form.

Amen Rad-Ghost.  We aren't counting schleptons at Fermi-Lab.  No reason to make things any more complicated.  Keep it simple, unless you are going for an MS or PhD.

[1010011010]

I'll join the "no such thing as deceleration" crowd.

I tend to think of Bremsstralung as a free state version of the photoelectric effect.

[alphadude]

hey we americans can change the language any way we wants too.. its good to be right....its our culture

Main Entry: de·cel·er·ate
Pronunciation: (")dE-'se-l&-"rAt
Function: verb
Inflected Form(s): -at·ed; -at·ing
Etymology: de- + accelerate
Date: 1899
transitive senses
1 : to reduce the speed of : slow down
2 : to decrease the rate of progress of
intransitive senses : to move at decreasing speed

bite my american ass

[RAD77DOG]

In the first quote on this subject from the "Moe Study Guide" by H.J. Moe; he appears to legitimize the term decelerate by using it in the text. Later he says "During this acceleration the electron may radiate energy of any amount from zero up to its total kinetic energy."  No matter if you call it deceleration or negative acceleration the electron will slow its velocity if it is giving up kenetic energy in the process of radiating energy, according to the law of conservation of energy. This means that while an electron may or may not accelerate when affected by the coulomb forces of a nucleus, it is only the loss of kinetic energy that produces the light.

[Rennhack]

No matter if you call it deceleration or negative acceleration

If they called it negative acceleration, we wouldn't be here talking about it.  They simply called it acceleration.

I just updated the original post with quotations from more texts.  (My HP library is ever growing).

[Fermi2]

Since it's defined in form of a physics term then any  change in the vector whether in direction of "speed" is acceleration. There is no such thing as decleration.

Mike

[Rennhack]

Since it's defined in form of a physics term then any  change in the vector whether in direction of "speed" is acceleration. There is no such thing as decleration.

Mike

If the majority of texts use the term decelerated, then it has to be a valid term to use in the description of this interation.

My bissue isn't with negative acceleration vs deceleration, I'm very clear, and fine with that.

My issue is with the NEU study guide NEVER using the word accelerated to describe the interaction.  Then the NEU test, which should be based on the study guide uses a description that is not in the study guide.  I think that is 'bunk'.

[hamsamich]

I think we are splitting hairs over terminology, but maybe for a dang good reason.  I know what the PHD will most likely be looking for: acceleration is positive or negative and is the only way to fly.  Maybe the problem is this: if you say you are decelerating at minus 32 ft/sec2, than what does this mean?  Does it mean - (-32), which is a +32, or does it mean (-32)?  And then, what does that mean if a body is exerting a force on another body and the vector is constantly changing; for instance:  a body was traveling at 6 ft/sec Southbound, and a force caused it to now be heading 6 ft/sec Northbound; when was it decelerating and when wasn't it?, since it is traveling in a whole different direction now.  When it was going precisely 0 ft/sec and some Northbound vector, do we all of a sudden say the force is aceleration now?  This seems redundant and problematic terminology.  If you use one term, this may eliminate the error likely situation.  Just a thought.  I do think it is confusing and unfair on tests to use one and then the other, so the test needs to reflect the MOST (not always black and white) correct version and the study material needs to teach the same terminology as the test.

[Fermi2]

Texts can be incorrect. ASk a physicist they'll tell you there's no such thing. Anytime you are changing a component on the vector you are changing the vector itself. There's no such thing as deceleration.

Mike

[HydroDave63]

Texts can be incorrect. ASk a physicist they'll tell you there's no such thing. Anytime you are changing a component on the vector you are changing the vector itself. There's no such thing as deceleration.

Mike

the net effect of all the vector changes is a lower energy product at the end. Kinda like thermalizing a neutron. Are there neutrons that accelerate to relativistic speed by colliding with hydrogen??? Is it a crime to say it decelerates, which communicates the correct concept of reducing the energy by the change of vector etc, or simply that it's snob value for not knowing what exact term physicists use while clinking rings at the secret science tree house Lodge?

[rlbinc]

It may sound like legalese, but deceleration is simply a negative vector acceleration. (Deceleration is a rate of velocity change in the opposite direction - a positive value with an opposite vector)

A car is decelerating at 3 ft/ sec squared heading west is accelerating 3 ft/ sec squared east. It just hasn't stopped and changed direction yet. In this case Kinetic Energy is being dissipated as Thermal Energy (heat) in either the brake disks, or reverse spinning tires.

Likewise, our charged particle sheds Kinetic Energy by releasing Brehmstrahlung. 

[SloGlo]

I do think it is confusing and unfair on tests to use one and then the other, so the test needs to reflect the MOST (not always black and white) correct version and the study material needs to teach the same terminology as the test.

unfortunately, math (hence physics) is black and white.  there is no "most correct" term, simply the one that is correct.  ifen yinz lose points because you use the wrong term, it's no worse than if you lose points for using the wrong number.  use the correct number, get the problem write.  right down the correct word 'n get the problem solved.  dun deel.

[hamsamich]

sorry, not that simple. terminology is not math.  the english language as well as most languages, except dead ones, will and are at this very moment living and breathing (changing).  deceleration may be accepted by some people and not others.  even if you surveyed a hundred or so math proffesors and textbooks today and most of them agree, tommorrow is a different story. 2 + 2 will always equal 4, but the definition of deceleration will never stay put.

[SloGlo]

hamsamich..... yeah, it is.  teminology describes the function.  science is not a democracy. it duzant matter what "most people" say or think.  proof is in the proof.  "most people" usta think the whirled was flat.  good thing they weren't listened to by those who were involved with the sciences, huh?  perhaps we should consider the opposite of decelleration to be procelleration, with the lack of pro or de to be simply celleration?

[hamsamich]

sorry, science doesn't work that way either! and terminology isn't the same as a proof.  science is probably even more dynamic than terminology.  i wish things would stay put sometimes or be as black and white as we want them to be but they never will be....sorry about that.  the "they" is us.  have a look at a dictionary sometime from the 50s and compare it to one today.  people used to say the same thing about the world being flat, but now we know it isn't.

[Halcyon Daze]

For my money, language is the use of words to convey ideas, so the word that gets the point accross to the most people is the "right" one. You have to target your audience though, so if you're talking to a bunch of people with white coats and big heads, use "acceleration." If you're talking to a cross section of people, use "deceleration."

[SloGlo]

check yer ancient greeks 'n yule find yer modern math formula 'n functions 'n stuff.  'n when i go to da 50s, i don't see da diff.  still ain't got no fusion, but da fission math ' phizziks hold up.  lotsa statistics work comes outa that era two.  watt terminology changed?  now, da werds cool, rad, bad, etc may have taken on new meanings, but have they lost da originals?  i due knot think sew.

[Evilpixie]

I agree with Renhack, the NEU should not test on things that they do not adequately cover.  I remember the last time I took that test there were some questions I had issues with for the same reason.  It's like they had someone who is good at explaining things write the study material and for writing the test they hired a hygenically challenged scientist who lacks social graces, communication skills, deodorant and has it out for anyone taking the test.

Of course, it's been awhile since I took the test. 

Hmm... acceleration is a physical property.  A variable in physics.  A vector quantity that describes the rate at which an object changes its velocity.

Then, there is acceleration.  In everyday English it's used to describe a state of increasing speed.  It's what most peops are accustomed to. 

Acceleration in physics is much more than increasing speed.  Any change in the velocity of an object results in an acceleration: increasing speed, decreasing speed, or changing direction. The terminology for it hasn't changed since Newton... (at least), in calculus acceleration is the derivative of velocity.

I bet they didn't have anything in that training guide that made the distinction, huh?  That's wrong and rather unfair.
 

[RDTroja]

From 'YourDictionary.com" following a list of other definitions for 'Accelerate' mostly meaning 'to increase speed:"

Physics: To change the velocity of.

The same dictionary gives no physics definition of 'Decelerate.'

Since we are talking physics here, maybe we should be speaking in terms of Physics definitions, n'est pas?

Several people have already pointed out that accelerate means to change vector velocity... it does not mean increase or decrease, merely change. Others have pointed out that most people understand accelerate means to go faster and decelerate means go slower. This is true in everyday use, but physics is not every day use. You can get 100,000,000 people to agree that 'bad' means 'good' but that does not make it so. 'Common usage' is for art (or conversation), not science.

Bremsstrahlung is caused by acceleration. Period. If you don't understand the terminology, you don't understand physics.

[Charles U Farley]

Y(Eo) = 1/Eo ∫ dE E*Nbr(Eo,E) = 13/16 k*Z*Eo

[cincinnatinuke]

From 'YourDictionary.com" following a list of other definitions for 'Accelerate' mostly meaning 'to increase speed:"

Physics: To change the velocity of.

The same dictionary gives no physics definition of 'Decelerate.'

Since we are talking physics here, maybe we should be speaking in terms of Physics definitions, n'est pas?

Several people have already pointed out that accelerate means to change vector velocity... it does not mean increase or decrease, merely change. Others have pointed out that most people understand accelerate means to go faster and decelerate means go slower. This is true in everyday use, but physics is not every day use. You can get 100,000,000 people to agree that 'bad' means 'good' but that does not make it so. 'Common usage' is for art (or conversation), not science.

Bremsstrahlung is caused by acceleration. Period. If you don't understand the terminology, you don't understand physics.

So when the Navy uses the term "Accelerate Your Life" in its commercials, perhaps they want you to think in the common usage/art/conversation term, but may well in fact mean decelerate.  Could help explain all the field days, time underway, and periods of lonliness.

[hamsamich]

concepts are not terminology and never will be, they are the only thing that are truly right or wrong.  you can talk all day of how only the "correct scientist" uses the "correct terminology", but in the end terminology is all man-made.  concepts were there before anybody thought to name them.  can't anybody see the difference?  the words acceleration and deceleration are merely man made markers for the same concept, and which ever marker scientists prefer has nothing to do with the correctness of a concept.  if 100,000,000 people think a word means something, it DOES mean it means something, that is WHY language is living and breathing.  words, however scientific, mean something only because the human mind recognizes it as a marker for a concept.

acceleration is the most accepted and "most correct" word choice, I recognize that, but in no way do you not understand the CONCEPT of acceleration if you chose to use the term deceleration.  that is a fairly absurd statement.

[RDTroja]

if 100,000,000 people think a word means something, it DOES mean it means something, that is WHY language is living and breathing.

Conversational language changes with the times and opinions of people and is 'living and breathing' if you chose to use those (also incorrect) terms... and that is fine even though it creates a lot of confusion for people that speak english (probably other languages as well.) If people decide that 'bad' is 'good' or "fo' shizzle" means anything at all that is unfortunate, but accepted.

Scientific language changes if we learn something new that causes us to change our understanding of the subject matter and then only by concensus of the scientists. This is science, not conversation or any other art form. Yes, a scientist will understand if someone uses the term 'decelerate' and they will also recognize that the speaker has a limited understanding of the concept.

[hamsamich]

saying "language changing is incorrect" is a pretty narrow view of things. it's a good thing many of the world's most important scientists (einstein, newton, many others) didn't look at things the same way, whether it be science or language, or we would still be falling off the edge of the world after a few hundred miles of travel.

I don't think it is unfortunate that language changes and is living and breathing, if that is what you meant.  many people look at science as an art form.  string theory is cutting edge today and how much of that has been proven?

professionalization, terminology, and a concept will always be 3 different things giving words meaning and importance, even scientific ones.  if you ask 100 top scientists i bet they will all have different answers for the meaning of acceleration, deceleration, and the difference between the two.  things aren't as cut in stone as you think they might be, or maybe want them to be.

[RDTroja]

I never said "language changing is incorrect" so if you want to use quotes, you could at least quote something that I did say. Einstein, Newton, et. al. did look at things from a scientific view and found new things that required new language and convincd the rest of the scientific world that they were right (or reasonably close enough) to accept the ADDITIONS to the language that were required to express the new ideas. Technicaly, they didn't change anything... they just found a way to explain how things work. The other scientists acceptance of the concepts is key to any scientific endeavor, including the language used to describe it. And even though I am not quite old enough to have witnessed it myself, I am pretty sure no one really fell off the earth before scientists changed its shape.

I do not think that changing language in general is unfortunate, but some changes are, fo' shizzle. Breeding ignorance into the English language is IMHO fairly tragic. But that is another topic. As for string theory and other cuttting edge concepts, they too may require some additions to the scientific dictionary, proven or not. They certainly introduce new concepts and change the way we look at old ones. But they will not require scientists to accept random changes to the way they describe their science because someone in their 15 minutes of fame changes the way pop culture speaks.

And, I will take that bet about the scientists. They will understand what deceleration means but very likely not use it in their next published work.

[Halcyon Daze]

ahhh, but do any of us know if 'deceleration' was added to the language, or was the concept of 'acceleration' expanded to encompass all changes in velocity?

[hamsamich]

Halcyon Daze, that is the kind of stuff I am talking about.  Good question.  we could probably go to the oxford english dictionary and check it out.

I don't know what you said then Troja, sorry.  Fo shizzle, hmmm, how about mesmerize instead, or say jingo?  There are plenty of examples of words that have come about in the last 400 years that were not there before.  I don't understand what you think is incorrect concerning your other post; you'll have to rephrase for me.

Do you really think deceleration has been around for 15 minutes?  I doubt it.  I know what you are saying, but deceleration has been around as long as acceleration probably.

Yes, most scientists will use acceleration.  I'm just saying that although not perfect, it is not 100% wrong either.  And just because someone uses the term deceleration doesn't mean they don't know what they are talking about.  I guess I just don't like gatekeeping (professionalization) type words and others that throw stones concerning word usage.  We all know what deceleration means, and saying it is completely incorrect and the people who use it aren't on par with the rest of us physics studs just seems like that type of thing to me.  There have been plenty of times in history when the guys using the big words got it wrong, and then hid behind esoteric words in ivory towers.  Think midwives in the late 19th century or phrenology.  Maybe the word "acceleration" isn't a good example of this, but people that come out and say "you just can't use deceleration because it is not right', well, this rubs me the wrong way.  Why isn't it right?  Get of the high horse and instead of saying "you don't know what you are talking about because you didn't use the right word", try, this MIGHT be why most scientists don't use that word, but technically you are correct.

Sorry, the attitude coming from a few posters concerning this pet peave of mine left a bad taste in my mouth

[RDTroja]

I am not sure which button got pushed or by whom, but this has gotten so far off of the track that it started on as to be an entirely different subject all together.

I could care less what words people use to talk to one another in daily conversation. I do have a lot of respect for the English language and personally don't like the direction that the changes are taking, but that is just one person's opinion. I disagree with the 'dumbing-down' (coming soon to a dictionary near you) of America as demonstrated in pop-culture, but there it is.

What is not opinion is that purely from a scientific view (and last time I checked Physics was a science) acceleration is used to describe a change in velocity -- positive or negative, depending on the relative view.  So, if one is to ask what causes Bremsstrahlung, the answer is acceleration. But only if you want the answer in scientific terms. And since our industry deals chiefly with science, that is the answer that makes the most sense. Call it whatever you want, but if you care about giving the most accurate answer, call it acceleration. And that is the problem today -- not enough people care about much. Just another opinion, of course.

[hamsamich]

I can dig it.  But I think this type of thing has always been associated with acceleration and deceleration; people get hung up on whether the word is correct instead of the meat of the issue.

[Evilpixie]

ahhh, but do any of us know if 'deceleration' was added to the language, or was the concept of 'acceleration' expanded to encompass all changes in velocity?

According to dictionary.com: 
accelerate originated around 1515-1525; de+(ac)celerate in 1895-1900

[SloGlo]

Get of the high horse and instead of saying "you don't know what you are talking about because you didn't use the right word", try, this MIGHT be why most scientists don't use that word, but technically you are correct.

Sorry, the attitude coming from a few posters concerning this pet peave of mine left a bad taste in my mouth

try using "negative dpm" sum time to describe a count rate < background 'n see watt consensus yule build wit yer listeners.

[bsdnuke]

Bremmstrahlung means braking radiation hence, slowing down.

[illegalsmile]

Bremmstrahlung means braking radiation hence, slowing down.

uhhhh, i think everyone here understands that the beta bug slows down. the point of contention is if slowing down constitutes deceleration or negative acceleration......semantics really.

[HAIRDUDE]

Here's what I get from it all:
Beta particles pass by at such an angle to any given nucleus and are "sling-shot" to a speed greater than the speed of light. This basically is the equivalent of putting the particle on 'crank'. When it is free of the "sling-shot zone" it begins to rapidly decelerate and gives off some of it's kinetic energy as 'the glow' due to its inability to loose enough energy throyugh deceleration alone. Then there is the part about the 'underpants gnomes' ... but I promised I wouldn't talk about that ... 

HAIRDUDE

[NC Bound]

Bremsstrahlung
  Radiation emitted by a charged particle under acceleration. In particular, the term is used for radiation caused by decelerations (the word is German for braking radiation) when passing through the field of atomic nuclei (external bremsstrahlung). Radiation emitted by a charged particle moving in a magnetic field is called synchrotron radiation.
The energy emitted by an accelerated particle is proportional to 1/m2, with m the rest mass of the particle; bremsstrahlung therefore plays a particularly important role for light particles; up to energies of 100 GeV, bremsstrahlung contributes substantially to energy loss in matter only for electrons. At the critical energy  , for electrons approximately given by   MeV/Z, the average energy loss by radiation and by ionization is the same (Z is the atomic number of the traversed material).
The energy spectrum of  rays due to bremsstrahlung of electrons decelerated in the field of atomic nuclei depends on the energy levels of the atomic electrons, due to the screening effect they have on the moving particle, and on the particle velocity. The spectrum extends up to quanta of the energy of the moving particle. In the high-energy limit the probability density is given by
 
where k = radiated energy, x = path length, X0 = radiation length, and F is a slowly varying function not very different from unity, that can be approximated by
 
with R=1-k/E. 
To a reasonable approximation, the amount of energy radiated per energy interval is constant.
Integration of the above formula results in the average energy loss per unit length which comes out to be
 
(this is more or less the definition of the radiation length X0).
In the relativistic limit, the radiated energy is contained in a narrow cone of average half-angle
 
independent of radiated energy.
The term internal bremsstrahlung is used to describe the radiation of non-virtual quanta, i.e. photons or gluons, by particles participating in an interaction. The formulae given for internal bremsstrah lung in electron scattering in the relativistic limit are
 
 
where  is the square of the four-momentum transfer, m the particle mass and F(E,k) has been given above.
In high-energy physics, bremsstrahlung has been put to use in constructing photon beams. Coherent bremsstrahlung on crystals with incident energetic electron beams has produced photon beams with energies > 200 GeV/c

[SloGlo]

Ya gotta love these kinda posts...  now what color is green???

green iz dat part uva spectrum witch kin be found by squaring da inverse uva wavelangth expulsion (meashured by columbs per cc/4) phrum da collision of yellow 'n blu photons.   sheeesh..............

[Rennhack]

Here is an update, wikipedia has a good explanation:

Source: http://en.wikipedia.org/wiki/Bremsstrahlung


Bremsstrahlung from German bremsen "to brake" and Strahlung "radiation", i.e. "braking radiation" or "deceleration radiation"), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. The term is also used to refer to the process of producing the radiation. Bremsstrahlung has a continuous spectrum. The phenomenon was discovered by Nikola Tesla during high frequency research he conducted between 1888 and 1897.

Bremsstrahlung may also be referred to as free-free radiation. This refers to the radiation that arises as a result of a charged particle that is free both before and after the deflection (acceleration) that causes the emission. Strictly speaking, bremsstrahlung refers to any radiation due to the acceleration of a charged particle, which includes synchrotron radiation; however, it is frequently used (even when not speaking German) in the more narrow sense of radiation from electrons stopping in matter.

The word Bremsstrahlung is retained from the original German to describe the radiation which is emitted when electrons are decelerated or "braked" when they are fired at a metal target. Accelerated charges give off electromagnetic radiation, and when the energy of the bombarding electrons is high enough, that radiation is in the X-ray region of the electromagnetic spectrum. It is characterized by a continuous distribution of radiation which becomes more intense and shifts toward higher frequencies when the energy of the bombarding electrons is increased.

Outer Bremsstrahlung
"Outer bremsstrahlung" is the term applied in cases where the energy loss by radiation greatly exceeds that by ionization as a stopping mechanism in matter. This is seen clearly for electrons with energies above 50 keV.

Inner Bremsstrahlung
"Inner bremsstrahlung" is the term applied to the less frequent case of radiation emission during beta decay, resulting in the emission of a photon of energy less than or equal to the maximum energy available in the nuclear transition. Inner bremsstrahlung is caused by the abrupt change in the electric field in the region of the nucleus of the atom undergoing decay, in a manner similar to that which causes outer bremsstrahlung. In electron and positron emission the photon's energy comes from the electron/nucleon pair, with the spectrum of the bremsstrahlung decreasing continuously with increasing energy of the beta particle. In electron capture the energy comes at the expense of the neutrino, and the spectrum is greatest at about one third of the normal neutrino energy, reaching zero at zero energy and at normal neutrino energy.

Beta particle-emitting substances sometimes exhibit a weak radiation with continuous spectrum that is due to both outer and inner bremsstrahlung, or to one of them alone.


Secondary radiation
Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g. 32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g. Plexiglass (lucite), plastic, wood, or water; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.


Source: http://en.wikipedia.org/wiki/Bremsstrahlung

[B.PRESGROVE]

Bremsstrahlung is a type of "secondary radiation", in that it is produced as a result of stopping (or slowing) the primary radiation (beta particles). In some cases, e.g. 32P, the Bremsstrahlung produced by shielding this radiation with the normally used dense materials (e.g. lead) is itself dangerous; in such cases, shielding must be accomplished with low density materials, e.g. Plexiglass (lucite), plastic, wood, or water; because the rate of deceleration of the electron is slower, the radiation given off has a longer wavelength and is therefore less penetrating.

In the Nuke Pharmacy world I now work in we deal with this on a regular basis.  There are certain "doses", drugs, that once active cannot be put into a lead pig due to the increase in gamma radiation.  We inturn must use a thick plastic pig in order to transport the meds.  It was funny because on of the guys I work with didnt understand this consept and put the dose in a lead lined pig only to cause the 110 to start chirpin like crazy.  He of cousre thought he had contaminated the whole world, but after simple explaining he understood.  Great thread on this topic.  Not many folks understand this unless they have delt with it first hand.

[atomicarcheologist]

Bremsstrahlung
 

I noticed that all the formulae in this post have been eliminated.  Does anyone have them to post?

[Rennhack]

I noticed that all the formulae in this post have been eliminated.  Does anyone have them to post?

http://en.wikipedia.org/wiki/Bremsstrahlung