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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
Alpha particles are repelled by atomic nuclei because?
Alpha particles are repelled by atomic nuclei because alpha particles have a positive charge, and so do atomic nuclei. The positive charge on the surface of a nucleus will repel another positive charge, like an alpha particle, because of the law of electrostatics. That's the simple answer. And it is correct. But know this: Alpha particles were used in the early investigations of atomic structure and atomic interactions. The alpha particles were used to bombard atomic nuclei, and there are times when an alpha particle will be absorbed by an atomic nucleus. Somehow the laws of electrostatics took the day off, and the fact that absorption took place opens the door to discovery and discussion of other atomic forces. Word up.
Nobelium is an artificial chemical element, radioactive and unstable.
Nobelium was first and surely prepared in 1966 by Russian physicists from Dubna; another claim from American physicists (1958) was not accepted by IUPAC.
Nobelium was obtained using this nuclear reaction:
238 92U + 2210Ne → 260102No* → 254102No + 6 10n
Why is radioactive decay measured in half lifes?
The half-life forms a type of clock used to calculate time passed.
Alpha particles are the least penetrating, and are not able to pass through a single sheet of paper. Beta particles can penetrate through a sheet of paper, but not a piece of aluminum. Gamma rays can travel through both paper and aluminum and it takes dense material like lead to stop them or reduce their number.
Gamma rays are high energy electromagnetic rays.
What is the Half life of cocaine?
It's the time required for half of the amount of the drug currently in the body to be eliminated. Both metabolism and excretion tend to follow this sort of rate law, so it's a pretty good measurement of how long it will take the blood concentration of the drug in question to drop to half its current value.
Beta radiation is made up of what?
There are 3 different types of radioactive decay. alpha decay, beta decay and gamma decay.
alpha decay is composed of a helium nuclei, beta decay emit either electrons or positrons, and finally gamma decay in which high energy "rays" of photons. A positron is a positively charged electron (antimatter twin of the electron).
See the natural decay series of U-238 and others to see which daughters emit beta to alpha or gamma.
there is also the neutrino. I cant say we really know that much about it but basically it helps satisfy the law of conservation.
What is the symbol of Beta-particle?
The symbol for a beta particle is either β- or e-, representing an electron. Beta particles are high-energy, high-speed electrons emitted during the process of beta decay in certain radioactive nuclei.
What forces hold an atom's nucleus together?
The primary forces that hold an atom's nucleus together are the strong nuclear force, which is attractive and overcomes the electrostatic repulsion between positively charged protons, and the weak nuclear force, which is responsible for certain types of radioactive decay. These forces play a critical role in maintaining the stability of the atom's nucleus.
A positron is a positively charged electron. It's an antielectron - antimatter! The positron has a charge of +1 (just the opposite of the -1 of the electron), and a spin of 1/2 as an electron does. The mass of this elementary particle is about 9.103826 x 10-31 kg. The actual charge on this particle is about +1.602 x 10-19 coulombs. We write it as β+ or e+ in nuclear equations.
It was Paul Dirac who first theorized that it may exist back in 1928, and in 1932, Carl D. Anderson discovered and named the positron. How was it done? By allowing cosmic rays to pass through a cloud chamber shielded with lead and set up in a magnetic field, the electron-positron pairs that were sometimes created could be observed. Once created, the particles moved (curved) in opposite directions within the magnetic field. Simple and clever! It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it.
We should also note that the positron is emitted (positron emission) in beta plus decay, which is a form of radioactive decay. Pair production, the "conversion" of electromagnetic energy into a positron and an electron, is also a source of positrons. Regardless of the source, the positron will always seek to "combine" with any nearby electron with the mass of both particles being converted into electromagnetic energy (a pair of gamma rays). A more detailed description and some of the other characteristics of the positron can be found in the Wikipedia article on that subject. A link is provided below to that post and also to some Related questions that will aid in understanding this critter.
What are the Use and misuse of nuclear chemicals and their effects?
Nuclear chemicals can be used for generating electricity, medical treatments, and research. However, misuse can lead to environmental contamination, radiation exposure, and potential health hazards. Exposure to nuclear chemicals can result in radiation sickness, genetic mutations, and an increased risk of cancer.
How many neutrons are in uranium-235 and uranium-238 respectively?
The element uranium (U) has 92 protons in its nucleus. That's where its atomic number comes from. When we see an isotope of an element written in "standard" form, the element name or symbol will be followed by the atomic mass (atomic weight) of the isotope. This number is basically the number of protons and neutrons (called nucleons when they are in an atomic nucleus) in an atom. In this case, we have U-235 and U-238. In the first case, 235 - 92 = 143, so U-235 has 143 neutrons. In the second case, 238 - 92 = 146, so U-238 has 146 neutrons. See the Related Questions below for how to find the number of neutrons in any atom.
If you let your abuser back in your life how do you end it after one day?
You don't! You need a plan and this is a good way: Contact your local "Abused Women's Center" (and if you can't find one go to your local Mental Health Clinic and they will lead you in the right direction.) Make an appointment to see a counselor there and tell them your story. PHONE FROM A PAY PHONE OR CELL PHONE. They basically set things up for you and give you a "safe place" to stay, while also giving you psychological counseling and legal counsel if necessary. If you have children take them with you! When you have accomplished that, then say ABSOLUTELY NOTHING TO YOUR ABUSER OR ANY FAMILY MEMBER OR FRIENDS. You can contact family and just one trusted friend while in the "safe house" and you should, or they'll be worried sick about you. NEVER, BUT NEVER tell them where this safe house is because if the counselors finds out you will be kicked out! Pack a bag (taking only what is necessary) and hide it. Leave no phone messages that can be traced and delete EVERYTHING on your computer where you have been discussing your feelings or actions re the abuser. The reason you need counseling is you are a "victim." Yes, that's right! Abusers control their victims and take their dignity and self esteem away from them. I can't tell you how proud of you I am, that you are taking this big step to get away from your abuser. The true test is ... staying away from him or choosing another partner who is also an abuser. You may think you aren't going to go back and that no, you aren't going to chose another guy that will abuse you, but the percentages out there speak the truth. Over 85% of women go back to their abusers for several different reasons. You need to build your self confidence up and also realize the strengths within yourself and this is where the counseling service comes in. They will give you tools to live by. You will also meet other women in your predicament. If you think you are alone, you are not. There is an extremely high number of women abused out there, and the first step to having a good life is the one you are taking right now. Good luck God Bless Marcy
A dirty bomb is an explosive device designed to eject or spray radioactive material over a small area. It does not produce mass amounts of fallout compared to a traditional nuclear device, since there is no fission involved. A conventional explosive such as those used on Oklahoma City, Beirut or the first World Trade Center attack, if packed with powdered or pelleted radioactive material (strontium, plutonium, etc.) would eject that material into buildings, parks, streets and people in the surrounding area. While the immediate death count would be low, many people would suffer from radiation sickness. Cleanup would be massively expensive and time-consuming. An area of several square miles would likely be uninhabitable for years.
Potential terrorists would buy the material on the black market from sources such as former Soviet Union countries, North Korea or the Middle East. Getting it refined in secret would be somewhat difficult. Transporting it to the target area would also be hard but not impossible.
*** I agree with the first part of the above answer, however anyone who is even fairly determined can get radioactive material. it is found is some medical equiptment, and other sources. The radio active material can be put in a regular pipe, or car bomb. If exploded in a populated area it would spread the radioactive materiel over a large area. Large numbers of people would have increased rates of cancer and other radation sicknesses. Other people would likely be injured by the direct blast and first responders would be in danger when going into rescue the wounded. The history (discovery, one of them) did a show on what would happen if a terrorist attacked with either a dirty bomb or a full atomic bomb. They did a good job and it is worth watching.
How much graphite is used in a nuclear power plant per year?
United States nuclear power plants do not use graphite for operation and thus the answer is "none". Graphite is used in some reactor designs as a "moderator", which is the reactor feature that slows down neutrons so that the chain reaction will continue. US nuclear plants are "light water reactors" which means that they use regular water as the moderator. Canadian plants, for example, are "heavy water" plants which use duterium as a moderator. Chernobyl, the Ukranian plant that exploded in the 1980's, used graphite as a moderator.
How does the atomic bomb work?
Simple explanation:Conventional bombs explode as a result of chemical reactions, but the atoms themselves that make up the chemicals stay unchanged by those reactions. On the other hand, the "Atomic Bomb", also called a "Nuclear Bomb", is so named because it explodes as a result of reactions which actually do change the atoms. When those atoms are changed in this way, they create explosive energy as a direct result of the changes of the atoms.
Technical Answer: To explain how a nuclear weapon (sometimes called an atomic bomb) works, we need to jump around a bit to pick up the necessary ideas that we'll knit together to build this critter. We can start by separating the nuclear weapons into two basic types: there is the fission weapon and there is the fusion weapon. We'll start with the first one and go from there. But first we need to review some physics. Buckle up. Let's take a ride.
Among those quirky elements at the upper end of the periodic table we find a couple or three that are fissile. What that means is that if they capture a neutron, they can fission; the atomic nucleus can be broken apart. They also spontaneously fission, and they do this to some extent all the time. All the elements at the upper end of the periodic table are unstable and undergo radioactive decay; they have no stable isotopes. But this is just a "breakdown" of the nucleus and the ejection of a particle or two and some energy. Fission is actually a "splitting" of the nucleus of an atom. It breaks into "chunks" we call fission fragments. A neutron or two or three is also ejected in the event. You can imagine the violence of this phenomenon on the atomic scale. It's horrendous. A lot of energy is released, and this is the key to the use of these materials in a weapon.
When we consider the fissionable materials, there is a threshold called critical mass associated with them. When it is exceeded, that is, when we "put together" enough material to exceed the critical mass, the material will spontaneously begin to fission. This is because a tiny number of spontaneous fissions occur naturally all the time, and the neutrons released in these events, which always are occurring, will start a chain reaction. (This is actually how an atomic bomb blast or the chain reaction in a nuclear reactor begins.) Enough material is around, that so-called critical mass, that a chain begins spontaneously. There is no way to stop this from happening if critical mass is reached. It will always occur. But which elements do this?
It is uranium and plutonium that we are most familiar with as nuclear weapons materials. Let's just look at them. As regards uranium, only the specific isotope U-235 will work for this application. Over 99% of the uranium in the ground is U-238, and only a tiny portion of the metal is the isotope U-235. We have to refine the uranium to separate the tiny bit of that lighter isotope out to make a weapon. And that's no mean feat! It takes a lot of equipment and energy to process the material and concentrate the preferred isotope sufficiently. We call this process enrichment, and the finished product is enriched uranium. Plutonium is created by exposing uranium to the neutron flux in an operating nuclear reactor and letting it "soak up some neutrons" and transform into plutonium. This is the most common approach to obtaining weapons materials that the nuclear powers use. So we have our nuclear material, and all we need to do now is make a bomb.
There is a thing called "geometry" that we associate with nuclear weapons. It speaks to the sizes and shapes of the sub-critical masses of the fissionable material that we are using in the bomb. It will probably also include how they will be brought together to achieve critical mass. Certainly there will be some safety features associated with the geometry, the physical design of the bomb. Remember that if we put enough fissionable material together to cause a chain reaction to begin, lots of energy will be liberated very quickly. And this energy will serve to "push apart" the material that was brought together to create the critical mass. So just "joining together" sub-critical masses of material won't work for a bomb because the immediate release of energy will force the material apart. There are a couple of basic ways to arrange the sub-critical masses and "force" them together, but that's what will have to be done. The fissionable material will have to be "driven together" somehow to make it work well. This is where conventional explosives come into the picture.
In a bomb, the sub-critical masses will be "blasted together" by a chemical explosive, and this blast will "hold" the material together for a split second to let the chain build to criticality and beyond to the point where the chain is actually supercritical. Proper design and construction will permit a good "burn" of the nuclear material with a large resultant release of energy. A triggering mechanism will set off the conventional charges and they will drive the sub-critical masses together. The "assembled" mass will be a bit more than critical, and the spontaneous fissions that are always occurring in the material will initiate a chain reaction. Atoms will spontaneously fission, the neutrons released will be captured by other nuclei, and they in turn will fission releasing more neutrons. The chain has begun and expands almost instantly. The periods of time associated with the initiation and buildup of the chain are ridiculously short. It all basically happens "in an instant" and the weapon detonates. This is the fission weapon, and a fission weapon is needed to set off a fusion weapon.
In nuclear fusion, protons are fused together to form helium nuclei - at least in the simplest form, which is what is used here. That is how our sun is operating now. At least mostly. Later in the sun's life, the fusion of heavier nuclei will be more predominate. Then heavier still. Anyway, it takes a lot of energy to force hydrogen nuclei (the protons) together and fuse them. This happens in an environment of extreme heat. Only the heat of a nuclear blast can create enough energy here on earth to fuse quantities of hydrogen nuclei into helium nuclei. (This though the laser pumped fusion reactor is still being experimented with.) The fusion of hydrogen, the fusing of those two protons and a pair of neutrons, is the hydrogen bomb. We effectively build a fission bomb "around" a supply of "hydrogen" and set it off to create the fusion explosion. It's really a huge blast. And that's the long and short of it.
There are some other "exotic" weapons out there. The fission-fusion-fission weapon is one that takes it a step further. It just uses the fusion device to trigger another fission device which is built into it. It's really hairy. There are neutron bombs, too, which just pack more "neutron producing material" in the package to generate more neutron radiation to kill things without increasing blast damage - which is already substantial. We've paved the road for you and given you a map to get you started. Should you wish to continue on down it, there will be some school work you'll have to master to fully appreciate the in's and out's of these notoriously quirky devices. Oh, and don't think you'll be "tickling the dragon's tail" any time soon. It takes a PhD and a security clearance above "Top Secret" to even get on the reservation, let alone get in the door.
Naturally we have some links you can follow to learn more, and those links can be found below.
What are radiocarbon dating limitations?
- First, the size of the archaeological sample is important. Larger samples are better, because purification and distillation remove some matter.
- Second, great care must be taken in collecting and packing samples to avoid contamination by more recent carbon.
- Third, because the decay rate is logarithmic, radiocarbon dating has significant upper and lower limits. It is not very accurate for fairly recent deposits. In recent deposits so little decay has occurred that the error factor (the standard deviation) may be larger than the date obtained. The practical upper limit is about 50,000 years.
- Fourth, the ratio of C-14 to C-12 in the atmosphere is not constant. Although it was originally thought that there has always been about the same ratio, radiocarbon samples taken and cross dated using other techniques like dendrochronology have shown that the ratio of C-14 to C-12 has varied significantly during the history of the Earth. To compensate for this variation, dates obtained from radiocarbon laboratories are now corrected using standard calibration tables developed in the past 15-20 years.
What is radiocarbon dating of fossils?
Carbon atoms are contained in most cells of all living things on Earth. Most carbon atoms (98.89 percent) are called carbon-12 because they have 6 neutrons and 6 protons in their nuclei. Most of the remaining atoms (1.11 percent) have 7 neutrons along with their 6 protons and are called carbon-13 atoms, but a very small quantity (called a trace amount) of carbon atoms have 8 neutrons and 6 protons. These and are called carbon-14 atoms.
Carbon-14 atoms are radioactive and are referred to as radiocarbon. They are unstable, and decay slowly by releasing electrons before evolving into nitrogen-14 atoms. A living organisms constantly absorbs carbon in its body systems by respiration and processing nutrients, and the amount of carbon-14 it contains remains fairly constant for as long as it lives. The carbon-14 decays without being replaced after the organism dies and half of the carbon-14 nuclei will disintegrate in about 5,730 years. The amount of carbon-14 that has disintegrated in a fossilized organism can be calculated and used for determining its age.
Beta taxonomy is the study of organizing and classifying species within a particular group based on their morphological, genetic, and ecological characteristics. It focuses on describing and naming newly discovered species as well as revising the classification of existing species at a level higher than species.
How is the density at a compression in a compressional wave like the height of a transverse wave?
In a compressional wave, the density of the medium varies periodically as the wave travels through it. This variation corresponds to the peaks and troughs in a transverse wave, where the denser regions represent the peaks of compression and the less dense regions represent the troughs of rarefaction. However, in a compressional wave, this density variation occurs in the same direction as the wave propagation, whereas in a transverse wave it occurs perpendicular to the direction of wave propagation.
What type of nuclear radiation is emitted in Boron 12 to Carbon 2?
Boron-12 (12B) typically undergoes beta decay, where a neutron is converted into a proton, emitting an electron (beta particle) and an antineutrino. This transformation results in carbon-12 (12C). So, the nuclear radiation emitted in this process is a beta particle.
When U-238 decays to th-234 what has been emitted?
An Alpha particle, and associated gamma radiation from the excited nucleus.
What is neutron proton scattering?
Neutron-proton scattering refers to the interaction between a neutron and a proton. It involves the exchange of a virtual meson between the two particles, which allows them to interact through the strong nuclear force. Studying neutron-proton scattering can provide valuable information about the structure and interactions of the atomic nucleus.
After the second half-life of uranium, half of the original amount will remain. Therefore, if you start with 80 grams of uranium, after one half-life you would have 40 grams remaining, and after the second half-life, you would have 20 grams.
What is the half-life of a 200.0g sample of nitrogen-16 that decays to 12.5g of nitrogen-16 in 48s?
12.5g is 1/16th of 200g. The half-life decay series is 1/2, 1/4, 1/8, 1/16, etc. so four half-lives of nitrogen-16 must have elapsed on 48s, making one half-life 12 seconds.
This is inconsistent with the NNDC known data on nitrogen-16, which has its half-life at 7.13 seconds. Perhaps this was the result of an experiment? Perhaps the question was "made up" with invalid data?
