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Nuclear Physics
Most commonly known for its applications in nuclear energy and nuclear weapons, Nuclear Physics also has applications in medicine and archaeology. This category is for questions about the branch of physics that deals with the study of the forces, reactions, and internal structures of atomic nuclei, Nuclear Physics.
3,164 Questions
What is the half life of an Egyptian papyrus with 63 percent of its original carbon-14 atoms?
The question is improperly asked. Papyrus does not have a half-life. Carbon-14 does. Half-life is constant, not variable, in this case, about 5730 years.
So, the question would be more properly asked as "what is the age of an Egyptian papyrus with 63 percent of its original carbon-14 atoms?"
The equation for radioactive decay is...
AT = A0 2(-T/H)
... where A0 is the starting activity, AT is the activity at some time T, and H is the half-life, in units of T.
Substituting what we know, we get...
0.63 = (1) 2(-T/5730)
Solve for T...
log2(0.63) = -T/5730
T = -log2(0.63)(5730)
T = 3819 (conservatively rounded, T = 3800)
Cardiovascular scanning is the correct answer.
echocardiogram
Real time scan- type of scanning that uses ultrasonic technology with a display of both structure and motion with time.
The force of gravity between two objects is proportional to their masses and inversely proportional to the square of the distance between them.
What is the difference between transmission and emission tomography?
the transmission of radiation/energy refers to the fraction of incident radiation that is absorbed by and passes through a substance or body +++ whereas emission refers to the amount of thermal radiation released or given off by a substance. for a substance to emit energy it does not necessarily need to have absorbed from another source, it may as well be its own internal energy.for instance i myself emit energy to the surroundings all the time, thus im able to set off the PIR detectors inside the special light bulbs my mum installed outside the house. however, a body or substance can only be said to transmit energy if the energy has come from another source, been absorbed by the substance and allowed to pass through it. so its basically the fraction of the absobed energy that leaves the body without being captured.
hope this helps
After 28 years your sample halves, ie becomes 38 mg. In another 28 years it will have halved again to 19 mg, so your answer is 56 years
It may not seem important, but you should remember that your sample is not evaporating. The actual 76 mg sample will still have almost all of its mass after 56 years. But by that time only 19 mg of it will be strontium-90. The rest of the sample will still be there, but it will have become Zirconium-90 which is stable.
If things go according to plan, the neutron encounters a fissionable atomic nucleus and then undergoes what is called neutron capture. That's the next step in the process. The presence of that neutron in the nucleus destabilizes the nucleus (more than it already is as that nucleus is radioactive and unstable anyway). In an extremely short period of time the instability results in nuclear fission. The nucleus splits.
Is the energy released by the stars a result of fission reactions?
No. However, the stars do use a different form of nuclear energy, called nuclear fusion or fusion.
In fission, heavy elements such as uranium are broken down into smaller elements, releasing huge amounts of energy in the process. This is used in power plants on Earth and was used in the first nuclear bomb dropped on Hiroshima, Japan.
In fusion, however, light elements starting with Hydrogen, the most abundant element in the Universe, are actually fused together into heavier elements such as Helium. Stars use this because there is SO much Hydrogen in the universe, and stars are full of it. Fusion requires a tremendous amount of energy to kick-start, but in return an even more tremendous amount of energy is released. That is what powers the stars. Currently, it is believed that elements up to oxygen (8) exist in our Sun.
The half-life of a radioactive nuclide when 95% of it is left after one year is 13.5 years.
AT = A0 2(-T/H)
0.95 = (1) 2(-1/H)
ln2(0.95) = -1/H
H = -1/ln2(0.95)
H = 13.5
That the mass of a helium nucleus is larger than the mass of the hydrogen nucleus. Also, since the star uses this process to produce energy, that the helium atom has less energy than the original hydrogen atoms - and therefore also less mass.
Why didn't protons neutrons and electrons bind together immediately after the big bang?
it was too hot
What was the Manhattan Project?
The Manhattan Project was the top secret military endeavor to build, and detonate the first atomic bomb. It was based at Los Alamos, New Mexico and headed by Dr. J. Robert Oppenheimer. The completion came on July 16, 1945 when the team exploded the first Atomic Bomb (Gadget) on the St. Augustine Plain at what is now known as the Trinity site, in central New Mexico. This site is open to the public for escorted tours twice a year: the first weekend in April and the first weekend in October.
Development of the first U.S. nuclear weapons (Gadget, Little Boy, Fatman) was led by the U.S Army and Los Alamos National Laboratory. Dr. Oppenheimer was the lead scientist, General Groves was the commander and executive in charge.
The project employed a large number of people in other places such as Oak Ridge, Tennessee and Hanford, Washington, where the fissile materials (80% enriched uranium at Oak Ridge, plutonium at Hanford) were made.
It was the WWII codename from 1942 to 1947 for the creation of the Atomic Bomb which was a Joint Canadian, United Kingdom, and United States effort under the control of the US Army Corps of Engineers. It was termed the Manhattan Engineering District to mask the large expenditures needed. In truth it had little to do with the island of Manhattan or with Manhattan Kansas. It involved over 130,000 people and spent two billion US dollars at such diverse locations as Oak Ridge Tennessee, Columbia University, the University of California Berkeley, the University of Chicago, Hanford Washington, Wendover Utah, Wright Field Ohio, Muroc Army Airfield California (now Edwards AFB), and Los Alamos New Mexico.
The military Manhattan Project ended in 1947 when its responsibilities were turned over to the newly created civilian Atomic Energy Commission.
Does a particle need to have an electrical charge to be used in a particle accelerator?
Yes, a particle used in a particle accelerator must have a charge to be useful in the device.
Particle accelerators we use in high energy physics to investigate things all work by applying a moving or shifting magnetic field to accelerate charged particles. We speed these particles up by repeatedly "hitting" them with a magnetic field. Uncharged particles will not respond to this, and canot be used in the devices.
You did not provide the list of "the following". However, the answer to the question is moderation. Moderation is the process whereby the neutron is slowed down in order to facilitate its subsequent capture by the nuclei of the fuel.
Why the alpha particles could not smash the nucleus apart?
The alpha particle is positively charged (as is the nucleus) and is heavy compared with the neutron that is neutral and lighter than the alpha particle.
Another viewpoint:
It depends what experiment the question is about. For example, over a hundred years ago, Rutherford bombarded gold foil with alpha particles and some "bounced off" what we now call the nucleus of the atoms. However, about ten years later he did experiments in which alpha particles did indeed "split" atomic nuclei. So, sometimes alpha particles can certainly smash a nucleus apart.
Under which conditions is a nucleus unstable?
When certain combinations of protons and neutrons form an atomic nucleus, there is the possibility that the nucleus may be unstable. There may be too few or too many protons for the number of neutrons present, or there may be too few or too many neutrons for the number of protons present. In any case, if the nucleus is unstable, that nucleus is said to be radioactive. There is another case in which a nucleus can be unstable, and that is that it is simply too large to be able to stay together. Recall that nuclear binding energy holds atomic nuclei together, and it overcomes the electromagnetic repulsion of the positively charged protons to do this. But when atoms become "really big" as we see them at the top end of the periodic table, they are uniformly unstable. They are all radioactive and will eventually undergo nuclear decay of some kind. In a radioactive substance, the instability of the nuclei of the atoms will eventually "win out" over the binding energy holding the nuclei together, and the nucleus will "fall apart" or even "split" in some cases. Is there a "magic number" associated with the disproportionality that will tell us if a given atom is unstable? No, there isn't. We have to look at things on a case by case basis. Recall that atoms of the same element that have differing numbers of neutrons in them are isotopes of that element. And for a given element, some unstable isotopes exist. They may appear in nature, or we may see them in the physics lab. In addition to the existence natural or synthesized radioactive isotopes of the elements, some elements have no stable isotopes whatsoever. That means all isotopes of those elements are radioisotopes, and are radioactive. You probably recall the element technetium, which has no stable isotopes. That's an example, and we see more examples at the "top end" of the periodic table where the nuclei of the elements are huge. The binding energy or nuclear glue holding the nuclei together is losing ground to the repulsive forces of all the positively charged protons. Eventually we'll reach a point where a massive nucleus won't stay together, no matter what.
Which of these masses is the largest alpha particle antineutrino gamma radiation beta particle?
Alpha Particle
Can a virtual photon create muon antimuon and tau antitau pair instead of electron positron pair?
Yes, although the heavier pairs are less likely to be found, it is not impossible.
How did Ernest Rutherford first split the atom?
As a physicist at the University of Manchester, Ernest Rutherford studied alpha particle radiation, among other things.
Rutherford is credited with being the first scientist to "split the atom" in 1917 in a nuclear reaction between nitrogen and alpha particles.
14N + α → 17O + proton
Rutherford noticed that when an alpha emitter decayed in the presence of air, there was unidentified radiation that resulted. He investigated this and demonstrated that the alpha emitted when striking nitrogen would produce oxygen and hydrogen.
This was the first demonstration of changing one type of nucleus (element) into another through radiation.
What is the time needed for half of a radioactive isotope to break down to form daughter isotope?
It's called "half life".
What is the variance of a inverse gamma distribution with alpha equals 2?
When alpha is 2 or less than 2 the variance of the inverse gamma doesn't exist. That is why when the variance is defined for the inverse gamma it always says "for α > 2". It is also the case that when alpha is 1 or less the mean of the inverse gamma doesn't exist. In order to really undertand what it means to say the variance doesn't exist (or the mean doesn't exist) you need to understand the mathematical definition of the variance (and of the mean). I don't know how to add the necessary symbols to clearly explain this. However, just briefly, mathematically both the mean and variance of the gamma density are definite integrals over the support of the density, which is 0 to infinity. In general, sometimes a definity integral over an infinite range (negative and/or positive) exists and sometimes it doesn't. In the case of the definite integral for the variance on the inverse gamma, when alpha less than or equal to 2, this integral doesn't exist.
Low energy beta particles, say, from tritium, are called soft beta particles.
Why is radiation detection important?
There are a number of reasons that radiation detection is important. The primary one has to do with exposure to radiation by radiation workers and others. If we have the proper detection equipment and use it appropriately, we know what's going on radiation wise and can plan accordingly. That will allow us to keep folks from getting zapped excessively, and that's very important to everyone concerned. It's for sure that we need radiation detectors around nuclear reactors to aid in early warnings that something is wrong. Any place that works with nuclear materials better have detectors operating.
We also use radiation detection equipment to find "hot spots" and locate things we need to get bagged and tagged. There are still some sites where some radioactive materials have gotten "loose" and need to be recovered. In the lab, we need to identify different types of radiation and the energies associated with it, and this will let us identify which radioisotopes are emitting the radiation. This is good stuff to know if an investigator is attempting to find out what materials or substances are in a sample.
There are a number of other uses for radiation detection equipment, but the primary ones have to do with protecting people who work with radioactive materials, and with having detectors at entrances and exits to nuclear facilities to prevent nuclear materials from coming in or going out. As an aside, but directly related, a worker in a facility that had nuclear materials in it set off detectors when he was coming in to work. These detectors were working properly, and it was determined in follow up investigations that the individual was being exposed to radon at home! It was a nice catch by the nuclear monitoring team.
What are examples of mesons and baryons?
Baryons are particles composed of three, "color-neutralizing" quarks. Protons and neutrons are the most well-known examples.
Mesons are particles composed of a quark/antiquark pair. The pion is the best-known example.
