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Particle Physics
Relatively recent experimental results have confirmed what philosophers throughout history had theorized all along; that all matter is made up of elementary particles. Those curious about this cutting-edge field of physics known as particle physics should post their questions here, including those about fundamental particles, fundamental forces, Grand Unified Theories, and the extraordinary devices that have been or need to be engineered to research them.
3,842 Questions
What prevents two protons from combining?
the electromagnetic repulsion.
they are both positively charged particles, and just like putting the south ends of a magnet together, they are actually repelled.
what stops them from flying apart is the strong nuclear force. gravity is also an attractive force between them yet it is so weak that it is negligible when being compared to the electromagnetic repulsion.
How do particle accelerators work?
They accelerate particles using magnets. Once going at speed close to the speed of light, particles smash into each other. Accelerators are used to examine the properties of subatomic particles. There is an accelerator in Chicago called Fermilab, and another, larger on in Europe. See the large hadron collider for more info on current accelerators.
What subatomic particle carries a negative electric charge?
The electron is the most important subatomic particle with a negative charge. There are others, however.
Electron. Muon. Quarks: down, strange, and bottom.
electron
The charge of subatomic particles as proton?
The charge of a proton is +1 elementary charge, which is equivalent to approximately 1.6 x 10^-19 coulombs.
How many nutrons are in silver?
There are about 61 neutrons in silver. It actually has less electrons and protons than neutrons, since it only has 47 of them.
Positrons are anti-electrons. They're antimatter. They don't generally "hang around" in our "regular matter" universe very long. They can be created in a type of radioactive decay called beta plus decay. That means that any radioisotope that decays by beta plus means will create some.
We also find positrons here and there where high energy gamma rays are present. That's because gamma rays of sufficient energy will create electron-positron pairs (in an even called -- no surprise -- pair production) if those gamma rays pass close to atomic nuclei.
During stellar nucleosynthesis, the process powering most stars, positrons are created in astronomical numbers. These positrons are "contained" within the star and add energy to the fusion process within the star.
Because positrons find an electron to "combine" with in mutual annihilation, we don't "find" positrons around much. In an antimatter universe, they'd be circling the nuclei of antimatter atoms just like the electrons form up around the nuclei of the "regular" atoms in our universe.
A positron is created in a pair production event or in beta+ nuclear decay (which is called positron emission). It (the positron) appears "out of nowhere" with an associated electron under certain conditions in pair production. And in the nuclear decay schemes of some radionuclides, it is generated spontaneously within the (unstable) nucleus and exits that nucleus in the decay event. Curious? Let's look further.
In positron emission (beta+ decay), a proton in an atomic nucleus experiences a change mediated by the weak interaction (the weak force), and one of its up quarks is transformed into a down quark. The change results in the "conversion" of a proton into a neutron. This causes atomic number to go down by one because there is one fewer proton in the atomic nucleus than just before the event. Here's an example:
In the beta plus decay of carbon-11, a new element, boron-11, is created. A positron, a neutrino, and a gamma ray will be ejected from the nucleus. Here's the equation for it:
6C => 5B + e+ + ve + 0.96 MeV
An atom of carbon becomes an atom of boron. The e+ is the positron and the ve is the neutrino. The gamma ray has an energy of 0.96 MeV (million electron-volts). There aren't many nuclei that do this. It is only seen in carbon-11, potassium-40, nitrogen-13, oxygen-15, fluorine-18, and iodine-121. That's it. Beta+ decay isn't all that tough to understand. What about pair production?
Pair production is the "making" of a positron and an electron out of a high energy gamma ray. Both pair production and beta plus nuclear decay occur naturally, so the positron can be said to occur in nature. Remember that the positron is an antiparticle - it's antimatter - and it will, after appearing, slow down via scattering and will eventually combine with an electron in mutual annihilation. The positron has a short mean lifetime and a short mean path of travel. They usually don't last long after they're created. But lets look at the creation of the particle pair.
The energy of the photon that creates the electron pair must have must meet a minimum threshold. And the threshold energy necessary for this even to be possible is 1.022 MeV. That's a lot of energy, and all that energy will be converted into mass - the rest mass of the electron and the rest mass of the positron. Higher energy gamma rays might still initiate pair production, but the extra energy would be accounted for in the kinetic energies of the pair of particles produced.
A gamma ray of sufficient energy passes near an atomic nucleus and the pair is produced. Note that pair production is not the spontaneous "option" that high energy gamma rays have. The photons must pass close by an atomic nucleus for there to be a probability that pair production will occur. This is because momentum must be conserved, and the "assisting" nucleus will handle this chore.
We should also note that researchers using high powered lasers on gold target material are able to produce considerable quantities of positrons for research, and this work is continuing. Links are provided to associated Wikipedia articles and related questions.
What are the 3 sub atomic particles?
Positively charged protons
Neutral neutrons
Negatively charged electrons
Is a proton a subatomic particle?
Yes, a proton is considered a subatomic particle. The proton, the neutron and the electron are smaller than atoms (making them subatomic particles). Further, these three particles are considered the building blocks of atoms. There are other subatomic particles, and to learn more, begin by examining the proton, neutron and the electron and finding out what it is that makes them up.
Yes, protons are subatomic particles which are found in the nucleus of the atom and have a positive charge.
How many protons are in the Hg atom?
The element mercury (Hg) has 80 protons and 80 neutrons. It exists in several different isotopes which have different numbers of neutrons, however, the average number of neutrons in a mercury atom is 121. (The atomic weight is 200.59 which would require 80 protons and 120.59 neutrons, although of course every atom has only whole numbers of neutrons, you only get fractions because you are getting an average of different isotopes.)
The location of the strongest magnetic forces is the?
Suitable place to entrepreneur conditions to follows which product produces, how much demand in market? how to manage the product distributed in market. how should follows ethical decisions to under stand the present market situations.
How do you describe orbital or shell?
A probabilistic function that describes the possible positions of one of the sets of electrons 'orbiting' the nucleus of an atom. For instance, the oxygen atom has two such shells, one consisting of a 'cloud' of two electrons and the other of six. The shapes of the density functions of individual electrons in these shells vary in shape depending on which shell is involved.
What is potential difference of a monopole?
The simple answer: the potential at a point some distance, r from a monopole is
kQ / r,
where k is Coulumb's constant: 9.0E9
Q is the charge of the monopole
and r is the distance from the monopole. And how to get there: Since electric force is kq1q2/ r2, the electric field ( Force per charge) is kQ/r2. The voltage of a particle is defined to be the integral of the electric field with respects to r. Thus integrating you get the above equation.
Why are the outermost electrons of an atom important?
An element's group is defined by the number of electrons on the outer shell. For instance, Lithium is in Group One because it contains one electron in its outer shell while Neon is in Group 0 because it has zero on its outer shell.
Electrons are emitted from a conductor when the conductor is?
Conductors don't EMIT electrons (any more than any material), but they allow electrons to flow freely within themselves. That is called a current.
On that note, a current flows through a conductor when it is moved through a magnetic field. This is how generators work.
Any material can be made to emit electrons by adding electrons to it. That's like saying a full cup will emit water if more water is added to it.
ACTUALLY they are emitted. look it up.
Does an electron-positron collision violate the law of conservation of matter?
No, electron-positron collision does not violate the law of the conservation of matter. Momentum and charge are also conserved. Electrons and positrons can collide in what are called scattering events, and they can do this without necessarily undergoing mutual annihilation. Because both these little critters can exist as a wave (particle-wave duality), their behavior can be fairly easily assessed using a "basic tool kit" to analyze electromagnetic wave interaction. But electrons and positrons can annihilate each other rather than scatter. Annihilation doesn't violate the law of conservation of matter, either. And there's a reason for that. The "old" idea of the conservation of matter was that matter could neither be created nor destroyed. But we now know that matter can be converted into energy. That's what happens in annihilation. The article in Wikipedia on the annihilation event touches on electron-positron collision. And there is an article on electromagnetic scattering as well. They aren't that difficult to understand, and the curious person will find links to those posts below.
How are the wavelength and spin of a lepton related?
The wavelength of a lepton is inversely proportional to its momentum, which is related to its energy and mass. The spin of a lepton is a fundamental property intrinsic to the particle itself, independent of its momentum or wavelength.
What are the subatomic particals?
Subatomic particles are parts of the building blocks of our world. Atoms house protons, neutrons and electrons which are key examples of subatomic particles.
Protons, neutrons and electrons themselves are made of even smaller blips called quarks. These minute objects build up the world and control various things like the states of an object, whether it is hot or cold and other key natural events.
Only subatomic particle NOT found in the nucleus?
Electrons are the only subatomic particles that are not found in the nucleus of an atom. They orbit around the nucleus in specific energy levels.
Why are their neutrons if they don't do anything?
protons and electrons are attracted to each other and act as magnets when close but if they touch it is cattastrofic for the atom. neutrons are neutral and sit in the middle of the protons and electrons to stop their electric charges from touching each other. electrons have no electrical charge.
What is the mass of the subatomic particles?
It really depends on which particle you're speaking about because a proton has a different mass regarding the electron. and the proton and the neutron have bigger masses than photons, neutrinos, electrons, etc.
What does a current flow of electrons need?
Your question is not clear. A current is generated when a group of electrons flow through a conductor, and this happens when there is a potential difference between the 2 ends of the conductor.
If you want to know how can we start the flow of electrons it is by creating a potential difference in between the 2 ends of the conductor.
What is equal to the mass of a proton?
The neutron has about the same mass as the proton, each has a mass a tiny amount greater than 1 AMU (atomic mass unit). The neutron is the smallest bit more massive.
The electron has a mass of just a bit over 5/10,000ths of an AMU. Extremely less massive in comparison, isn't it!
== If the question can be imagined and framed properly, it can be asked, even if it has no "real world" applications. But let's get real with this one. The answer is "not very far" into the lead shield. A sheet of aluminum foil would stop the pair of particles. We've got problems with this one. There isn't a handy table for looking up the slowing down length of lead for positrons across a range of positronic energies, but let's take a short detour. We need some review. A positron and an electron are created in pair production. You're already fairly familiar with the electron. It has a negative charge, doesn't weigh very much (has little mass), and when it's moving, it will have to contend with the orbiting electrons of all the atoms in its path of travel. (Even in air, there are a tons and tons of "speed bumps" in the way of our little electron.) The electron can't cope well with these "flocks" of critters of its own kind, even if it is of high energy. It will scatter and lose energy at just about every atom it encounters along its trajectory (if we can use that term). It takes little time, that is, it can't travel very darn far, before the "encounters" it has with anything it "bumps into", i.e., those scattering events, "suck" all the energy out of our little electron and it's left hanging. It has a very short mean free path in air. In any kind of liquid or solid, it's even shorter. A lot shorter. And it's the same with a positron - except that it will join an electron at some point along its journey and the pair will be mutually annihilated. A couple of hot gamma rays will leave the scene of the event. Even with a few MeV of energy, the mean free path of an electron and a positron is extremely short in air. Oh, and these particles will be traveling in oppositedirections when they are created. It isn't like they'd be moving as a pair in the same direction like cars in adjacent lanes on a freeway. What about plumbum? We're talking mean free path here - the mean free path of an electron and a positron in lead. What is the slowing down length for a positron or an electron at a couple of MeV in lead? Short. Very short. Very, very short. Laying out the problem mathematically would just be an exercise in probability and statistics. And forget about setting up an experiment to "prove" the calculated answer. Got a clever little application for running Monte Carlo calculations on your computer? Start identifying and defining your variables. And don't forget to include factors that deal with both inelastic andelastic scattering. You'll have both happening here 'cause it's "real world" stuff. So no fudging and leaving out elastic scattering possibilities. It's a physics grad student's nightmare. Good luck with all that. What about conducting an experiment? The only thing close to being effective at "looking" at the penetration power of the positron is probably a spectroscope or PET imager, but how are you going to use them? The spectroscope would be difficult to apply for the purpose here (impossible, probably), and the PET units can't "resolve" the tiny distances we're talking about. By the way, it is true that you'd only be looking at the annihilation events resulting from the positron's recombination with an electron in PET imaging. And the ability of those machines is a long way from having the kind of resolution you'd need to "see" results that you could measure. You'd doubtless have better luck with just calculating an answer.
