All exercise Short Questions of Theories of Radioactive Decay of book Nuclear Physics for BS/MSc Physics students.
Q.1 What is radioactivity in simple words?
Answer. radioactivity. The emission of elementary particles by some atoms when their unstable nuclei disintegrate (see half-life). Materials composed of such atoms are radioactive.
Q. What is radioactivity and its types?
Radioactive decay occurs in unstable atomic nuclei – that is, ones that don’t have enough binding energy to hold the nucleus together due to an excess of either protons or neutrons. It comes in three main types – named alpha, beta and gamma for the first three letters of the Greek alphabet.
Q.2 What is the difference between radioactivity and radioactive decay?
Answer. Radioactivity is the term given to the breaking-up (decay) or rearrangement of an atom’s nucleus. Decay occurs naturally and spontaneously to unstable nuclei. … gamma decay: the protons and neutrons within the nucleus rearrange into a more stable form, and energy is emitted as a gamma ray.
Q.3 What does it mean to be radioactive?
Answer. Isotopes that are unstable, meaning they have an imbalance of neutrons and protons are radioactive. They release this extra energy and over time radioactively decay to a stable isotope. Radioactive materials occur naturally but are also man-made.
Q.4 What is radioactivity and examples?
Answer. One example of a radioactive substance is uranium. In nuclear power plants, uranium is used to produce electricity. When radioactive substances like uranium produce radiation, they also create a lot of heat.
Q.5 How does radioactivity kill you?
Answer. Ionizing radiation—the kind that minerals, atom bombs and nuclear reactors emit—does one main thing to the human body: it weakens and breaks up DNA, either damaging cells enough to kill them or causing them to mutate in ways that may eventually lead to cancer.
Q.6 What are the uses of radioactivity?
Answer. Radioactivity tracers are commonly used in the medical field and also in the study of plants and animals. Radiation is used and produced in nuclear reactors, which controls fission reactions to produce energy and new substances from the fission products.
Q.7 Can a person be radioactive?
Answer. How Radioactive Contamination Is Spread. … People who are internally contaminated can expose people near them to radiation from the radioactive material inside their bodies. The body fluids (blood, sweat, urine) of an internally contaminated person can contain radioactive materials.
Q.8 Are bananas radioactive?
Answer. Bananas are slightly radioactive because they contain potassium and potassium decays. Potassium is a necessary substance for healthy operation of your body. You would have to eat a LOT of bananas just to compete with the natural potassium dose of your body.
Q.9 Can bananas kill you?
Answer. The fear that bananas can kill is a surprisingly resilient one. It takes two forms: they can give you a fatal overdose of potassium, or a deadly dose of radiation. On the first matter, it is well-known that bananas contain potassium, and this is a good thing.
Q.10 Are bananas radioactive death?
Answer. Yes, bananas are radioactive, but so are you. Yes, you will certainly die from radiation poisoning if you are able to eat 10,000,000 bananas at once. You may also witness chronic symptoms if you eat 274 bananas a day for seven years.
Q.11 Is the sun radioactive?
Answer. The core of the sun – where nuclear reactions produce neutrinos – apparently spins more slowly than the surface we see. … All of the evidence points toward a conclusion that the sun is “communicating” with radioactive isotopes on Earth, said Fischbach.
Q.12 What are the 5 types of radiation?
Answer. This includes:
- electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ)
- particle radiation, such as alpha radiation (α), beta radiation (β), and neutron radiation (particles of non-zero rest energy)
Q.12 How radioactive is a person?
Answer. The major one that produces penetrating gamma radiation that can escape from the body is a radioactive isotope of potassium, called potassium-40. … The amount of the radioactive isotope 40K in a 70-kg person is about 5,000 Bq, which represents 5,000 atoms undergoing radioactive decay each second.
Q.13 How long does radiation take to kill you?
Answer. If 100 people get a sudden dose of 350 rems of radiation, about 3.5 sieverts, then about half of them will die in 60 days. 350 rems is considered LD50/60. It means what you think. 50% death rate in 60 days.
Q.14 Why is potassium 40 radioactive?
Answer. Potassium–40 (40K) is a radioactive isotope of potassium which has a very long half-life of 1.251×109 years. It makes up 0.012% (120 ppm) of the total amount of potassium found in nature. … Very rarely (0.001% of the time) it will decay to 40Ar by emitting a positron (β+) and a neutrino.
Q.15 When did the explosion in Chernobyl happen?
Answer. 26 April 1986
The Chernobyl disaster was a catastrophic nuclear accident that occurred on 26 April 1986 at the No. 4 nuclear reactor in the Chernobyl Nuclear Power Plant, near the city of Pripyat in the north of the Ukrainian SSR.
Q.16 Who discovered radioactive decay?
Answer. Henri Becquerel
In the 19th century, Henri Becquerel discovered that some chemical elements have atoms that change. In 1898, Marie and Pierre Curie called this phenomenon radioactive decay.
Q.17 How many nuclear reactors have exploded?
Answer. Fifty-seven accidents have occurred since the Chernobyl disaster, and almost two-thirds (56 out of 99) of all nuclear-related accidents have occurred in the US. There have been comparatively few fatalities associated with nuclear power plant accidents.
Q.18 What radiation do bananas emit?
Answer. Dose calculation, Plants naturally contain radioactive carbon-14 (14C), but in a banana containing 15 grams of carbon this would give off only about 3 to 5 beta rays per second. Since a typical banana contains about half a gram of potassium, it will have an activity of roughly 15 Bq.
Q.19 Is potassium hard or soft?
Answer. Potassium is the second least dense metal after lithium. It is a soft solid with a low melting point, and can be easily cut with a knife.
Q.20 What does it mean when an element has a half-life?
Answer. In particular then, the half life of a radioactive element is the time required for half of it to decay (i.e. change into another element, called the “daughter” element). So if a radioactive element has a half life of one hour, this means that half of it will decay in one hour.
Q.21 Why do we use half-life?
Answer. We use the half–life because radioactive decay is a matter of chance. When one atom will decay is anyone’s guess. If you have two identical atoms, one could decay immediately, the other could hang around for a century or a millennium. … This time frame, where statistically half the atoms decay is called the half–life.
Q.22 What does the half-life symbol mean?
Answer. The Lambda logo (λ) is a symbol found frequently in the Half–Life universe. It represents the Greek letter “Λ” (lowercase “λ”), and is a radioactive decay constant used in the half–life equation. “Λ” is the 11th letter in the Greek alphabet.
Q.23 How do scientists determine half-life?
Answer. The half-life of a radioactive isotope is the amount of time it takes for half of the isotopes to decay. However, you do not need to wait the whole half-life to measure decay. … After only 1/2 of a half life, 0.29 (or 29%) of the radioactive atoms have decayed but 0.71 (or 71%) of them still remain.
Q.24 What happens in alpha decay?
Answer. Alpha decay occurs when a nucleus is unstable because it has too many protons. The Figure below shows what happens during alpha decay. The nucleus emits an alpha particle and energy. An alpha particle consists of two protons and two neutrons, which is actually a helium nucleus.
Q.25 How does alpha decay work?
Answer. Alpha decay is one process that unstable atoms can use to become more stable. During alpha decay, an atom’s nucleus sheds two protons and two neutrons in a packet that scientists call an alpha particle. Since an atom loses two protons during alpha decay, it changes from one element to another.
Q.26 What is the cause of alpha decay?
Answer. Alpha Decay. In alpha decay, shown in Fig. 3-3, the nucleus emits a 4He nucleus, an alpha particle. Alpha decay occurs most often in massive nuclei that have too large a proton to neutron ratio. … Alpha radiation reduces the ratio of protons to neutrons in the parent nucleus, bringing it to a more stable configuration.
Q.27 What is alpha and beta decay?
Answer. Beta decay is somewhat more complex than alpha decay is. These points present a simplified view of what beta decay actually is: 1) A neutron inside the nucleus of an atom breaks down, changing into a proton. 2) It emits an electron and an anti-neutrino (more on this later) which go zooming off into space.
Q.28 What is the formula for alpha decay?
Answer. During α–decay, an atomic nucleus emits an alpha particle. It transforms (or decays) into an atom with an atomic number 2 less and a mass number 4 less. Thus, radium-226 decays through α–particle emission to form radon-222 according to the equation: 22688Ra → 22286Rn+42He.
Q.29 What are two elements that go through alpha decay?
Answer. kmatras1. Two elements that go through alpha decay are uranium and thorium. Alpha decay happens when a particle of two protons and two neutrons is emitted from a radioactive atom’s nucleus. This only occurs in heavy elements, which is why uranium and thorium qualify.
Q.30 What force is responsible for alpha decay?
The weak nuclear force is responsible for all three types of nuclear decay; Alpha, Beta or Gamma. Alpha decay is the emission of a helium nucleus from an atom, Beta decay is when an electron or positron is emitted from an atom, and Gamma decay is the emission of a high energy photon from an atom.
Q.31 How are alpha particles formed?
Answer. Alpha “rays” are actually high speed particles. Early researchers tended to refer to any form of energetic radiation as rays, and the term is still used. An alpha particle is made up of two protons and two neutrons, all held together by the same strong nuclear force that binds the nucleus of any atom.
Q.32 Where do alpha particles come from?
Answer. Alpha particles (a) are composite particles consisting of two protons and two neutrons tightly bound together (Figure 1). They are emitted from the nucleus of some radionuclides during a form of radioactive decay, called alpha-decay.
Q.33 Are alpha particles dangerous?
Answer. Due to the short range of absorption and inability to penetrate the outer layers of skin, alpha particles are not, in general, dangerous to life unless the source is ingested or inhaled.
Q.34 What is the difference between alpha beta and gamma decay?
Answer. Alpha decay forms new element with two fewer protons and two fewer neutrons; Beta decay forms new element with one more proton and one fewer neutron. Gamma decay forms NO new element, but now the element has less energy because energy is released as gamma rays.
Q.35 What can alpha decay penetrate?
Answer. The penetrating power of alpha rays, beta rays, and gamma rays varies greatly. Alpha particles can be blocked by a few pieces of paper. Beta particles pass through paper but are stopped by aluminum foil. Gamma rays are the most difficult to stop and require concrete, lead, or other heavy shielding to block them.
Q.36 Does alpha decay release electrons?
Answer. In alpha decay process, parent nucleus decays by emitting alpha and daughter nucleus. However, It is the decay that happens in parent atom. … If it is correct, which means that the daughter “atom” remains two extract electrons after alpha decay.
Q.37 What particle is emitted in beta decay?
Answer. In positron emission, also called positive beta decay (β+–decay), a proton in the parent nucleus decays into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron, which is a positive particle like an ordinary electron in mass but of opposite charge.
Q.38 What is the symbol for alpha radiation?
Answer. Alpha, beta and gamma
| Type of radiation | Greek symbol | Charge |
| Alpha | α | Positive 2+ |
| Beta | β | Negative 1- |
| Gamma | γ | No charge |
Q.39 Why do heavy elements decay?
Answer. Reason why heavier nuclei are more unstable lies in electrostatic repulsion of protons, which is stronger than the nuclear force at longer distances. … Beta decay commonly occur in isotopes of very light elements and is not based on the mass of a nucleus, but alpha decay is only possible for the very heavy elements.
Q.40 What elements go through beta decay?
Answer. Beta decay is one process that unstable atoms can use to become more stable. There are two types of beta decay, beta-minus and beta-plus. During beta-minus decay, a neutron in an atom’s nucleus turns into a proton, an electron and an antineutrino.
Q.41 What force is responsible for beta decay?
Answer. The role of the weak force in the transmutation of quarks makes it the interaction involved in many decays of nuclear particles which require a change of a quark from one flavor to another. It was in radioactive decay such as beta decay that the existence of the weak interaction was first revealed.
Q.42 What force causes gamma decay?
Answer. Gamma decay occurs when there is too much energy in the nucleus of an atom, causing it to emit a gamma-ray without changing its charge or mass composition.
Q.43 What is emitted when an isotope undergoes alpha decay?
Answer. In alpha decay, energy and an alpha particle are emitted by a nucleus that is unstable because it has too many protons. An alpha particle consists of two protons and two neutrons, so it is actually a helium nucleus. Alpha decay is represented by a nuclear equation.
Q.44 What can stop an alpha particle?
Answer. Alpha particles can be stopped by a sheet of paper, beta particles by aluminum, and gamma radiation by a block of lead.
Q.45 How are alpha particles detected?
Answer. It detects ionizing radiation such as alpha particles, beta particles, and gamma rays using the ionization effect produced in a Geiger–Müller tube, which gives its name to the instrument.
Q.46 What would happen if alpha particles hit electrons while emitting from a nucleus?
Answer. It is an important mode by which charged particles lose energy while passing through matter. So when a alpha particle is passing in the vicinity of electrons of the atoms in the material it can ionize the atoms and lose energy thereby.
Q.47 What happens when a beta particle is emitted?
Answer. Beta decay occurs when a nucleus is unstable because it has too many or too few neutrons relative to protons. The nucleus emits a beta particle and energy. … In beta-minus decay, a neutron breaks down to a proton and an electron, and the electron is emitted from the nucleus.
Q.48 Why is an antineutrino emitted in beta decay?
Answer. Positron and Neutrino
The emission of a positron or an electron is referred to as beta decay. The positron is accompanied by a neutrino, an almost massless and charge less particle. Positrons are emitted with the same kind of energy spectrum as electrons in negative beta decay because of the emission of the neutrino.
Q.49 What happens in beta plus decay?
Answer. In positron emission, also called positive beta decay (β+–decay), a proton in the parent nucleus decays into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron, which is a positive particle like an ordinary electron in mass but…
Q.50 What is the formula for beta decay?
Answer. For example, carbon-14 is a radioactive isotope of carbon. It decays by beta minus emission. The equation for this decay is: Notice that the atomic mass number is unchanged (because a neutron changed into a proton) and that the atomic number has gone up by one (it has gained a proton).
Q.51 What is gamma decay?
Answer. Gamma decay, type of radioactivity in which some unstable atomic nuclei dissipate excess energy by a spontaneous electromagnetic process. In the most common form of gamma decay, known as gamma emission, gamma rays (photons, or packets of electromagnetic energy, of extremely short wavelength) are radiated.
Ernest Rutherford
Rutherford’s Discovery of Alpha and Beta Radiation. By 1898, Becquerel had switched his research interests to the Zeeman effect (which was also discovered in 1896, the year of radioactivity’s discovery). Ernest Rutherford, a student of J.J. Thomson, decided to begin research into radioactivity.
Q.52 What is the decay rate formula?
Answer. In mathematics, exponential decay describes the process of reducing an amount by a consistent percentage rate over a period of time and can be expressed by the formula y=a(1-b)x where in y is the final amount, a is the original amount, b is the decay factor, and x is the amount of time that has passed.
Q.53 What particle is emitted in gamma decay?
Answer. Types of radioactive decay include alpha, beta, and gamma decay. In alpha and beta decay, both particles and energy are emitted. In gamma decay, only energy, in the form of gamma rays, is emitted.
Q.54 What does gamma decay mean?
Answer. Gamma decay, type of radioactivity in which some unstable atomic nuclei dissipate excess energy by a spontaneous electromagnetic process. In the most common form of gamma decay, known as gamma emission, gamma rays (photons, or packets of electromagnetic energy, of extremely short wavelength) are radiated.
Q.55 How is gamma decay useful?
Answer. Gamma–rays have the smallest wavelengths and the most energy of any other wave in the electromagnetic spectrum. These waves are generated by radioactive atoms and in nuclear explosions. Gamma–rays can kill living cells, a fact which medicine uses to its advantage, using gamma–rays to kill cancerous cells.
Q.56 Who discovered gamma decay?
Answer. Paul Villard
History of discovery
Paul Villard, a French chemist and physicist, discovered gamma radiation in 1900, while studying radiation emitted from radium.
Q.57 What does gamma look like?
Answer. Gamma. Gamma (uppercase/lowercase Γ γ), is the third letter of the Greek alphabet, used to represent the “g” sound in Ancient and Modern Greek. In the system of Greek numerals, it has a value of 3.
Q.58 Why is gamma decay dangerous?
Answer. If the radioactive source is outside the body:
alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body. beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside.
Q.59 How do you measure decay?
Answer. To find the amount for any time period, multiply the time period by the decay rate and raise e, the natural logarithm base, to the power of the result. Then take that answer and multiply it by the initial value.
Q.60 What is the exponential decay model?
Answer. A model for decay of a quantity for which the rate of decay is directly proportional to the amount present. … This model is used for phenomena such as radioactivity or depreciation. For example, A = 50e–0.01t is a model for exponential decay of 50 grams of a radioactive element that decays at a rate of 1% per year.
Q.61 What is a decay curve?
Answer. decay curve A graphical representation of the exponential rate at which radioactive disintegration occurs (see RADIOACTIVE DECAY). … A plot of the surviving parent atoms against time in half-lives (see DECAY CONSTANT) gives a decay curve that approaches the zero line asymptotically.
Q.62 What is the rate of decay of carbon 14?
Answer. If the amount of carbon 14 is halved every 5,730 years, it will not take very long to reach an amount that is too small to analyze. When finding the age of an organic organism we need to consider the half-life of carbon 14 as well as the rate of decay, which is –0.693.
Q.63 Are gamma rays a form of light?
Answer. Other types of nonvisible light include x-rays, ultraviolet light, infrared radiation, and radio waves. Gamma rays are the most energetic. Gamma rays occupy the short-wavelength end of the spectrum; they can have wavelengths smaller than the nucleus of an atom.
Q.64 What is gamma irradiation used for?
Answer. Gamma Irradiation Processing. The gamma sterilization process uses Cobalt 60radiation to kill microorganisms on a variety of different products. Processing with gamma irradiation yields quick turnaround time, easily penetrating packaging and product, and is ideal for many types of materials.
Q.65 How do gamma rays kill cancer cells?
Answer. Radiation therapy uses high-energy particles or waves, such as x-rays, gamma rays, electron beams, or protons, to destroy or damage cancer cells. Your cells normally grow and divide to form new cells. But cancer cells grow and divide faster than most normal cells.
Q.66 What is random nature of decay?
Answer. Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles (radiation). … This is a random process, i.e. it is impossible to predict the decay of individual atoms.
Q.67 Why do scientists specifically use carbon 14 radioactive dating?
Answer. Because carbon–14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon. The carbon–14 method was developed by the American physicist Willard F. Libby about 1946.
Q.68 What is the process of carbon dating?
Answer. Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. … The development of radiocarbon dating has had a profound impact on archaeology.
Q.69 Why is it called gamma rays?
Answer. The key difference between gamma rays and X-rays is how they are produced. Gamma rays originate from the settling process of an excited nucleus of a radionuclide after it undergoes radioactive decay whereas X-rays are produced when electrons strike a target or when electrons rearrange within an atom.
Q.70 How many died in Chernobyl?
Answer. The resulting steam explosion and fires released at least 5% of the radioactive reactor core into the atmosphere and downwind – some 5200 PBq (I-131 eq). Two Chernobyl plant workers died on the night of the accident, and a further 28 people died within a few weeks as a result of acute radiation poisoning.
Q.71 Are gamma rays visible to the human eye?
Answer. There are radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays and gamma rays, all of which form what is known as the ‘electromagnetic spectrum’. Oddly enough, visible light – to which human eyes are sensitive – is the smallest band of radiation
Q.72 What is meant by quantum tunneling?
Answer. Quantum tunneling or tunneling is the quantum mechanical phenomenon where a subatomic particle passes through a potential barrier. … The effect was predicted in the early 20th century, and its acceptance as a general physical phenomenon came mid-century.
Q.73 What causes quantum tunneling?
Answer. A tunneling current occurs when electrons move through a barrier that they classically shouldn’t be able to move through. … When an electron moves through the barrier in this fashion, it is called tunneling. Quantum mechanics tells us that electrons have both wave and particle-like properties.
Q.74 Is quantum tunneling instantaneous?
Answer. Quantum tunneling seems to happen instantaneously – or at least, so incredibly quickly that it’s essentially instantaneous. According to the researchers, it takes less than 1.8 attoseconds, which is a billionth of a billionth of a second.
Q.75 What is a quantum barrier?
Answer. Rectangular potential barrier. From Wikipedia, the free encyclopedia. In quantum mechanics, the rectangular (or, at times, square) potential barrier is a standard one-dimensional problem that demonstrates the phenomena of wave-mechanical tunneling (also called “quantum tunneling”) and wave-mechanical reflection.
Q.76 What is an energy well?
Answer. A potential well is the region surrounding a local minimum of potential energy. Energy captured in a potential well is unable to convert to another type of energy(kinetic energy in the case of a gravitational potential well) because it is captured in the local minimum of a potential well.
Q.77 What is the use of neutrino?
Answer. A way to monitor nuclear proliferation.
Neutrinos are produced from radiation, so it might be possible for the International Atomic Energy Agency to use neutrino detectors to monitor which countries are following the treaty on the Non-Proliferation of nuclear weapons.
Q.78 Why are neutrinos important?
Answer. Neutrinos are very important to the study of supernovas because they provide an early warning signal and allow scientists to be looking in the right direction before the supernova even takes place.
Q.79 Why is a neutrino emitted in beta decay?
Answer. Positron and Neutrino
The emission of a positron or an electron is referred to as beta decay. The positron is accompanied by a neutrino, an almost massless and chargeless particle. Positrons are emitted with the same kind of energy spectrum as electrons in negative beta decay because of the emission of the neutrino.
Q.80 Are neutrinos affected by gravity?
Answer. Because neutrinos are particles and have mass then yes, they are affected by gravity. … Since we can see that photons bend their stream while passing planets and other large gravitational masses it lends credence to the idea that invisible neutrinos will bend in gravitational fields as well.
Q.81 How do neutrinos affect humans?
Answer. Millions of neutrinos coming from nuclear reactions in the Sun pass through our body every day without ill effects. The reason is that their interaction with human tissue is next to zero. All charged particles, like electrons, protons, etc do interact and in sufficient quantities can be harmful.
Q.82 Can neutrinos be used for energy?
Answer. The neutrinos themselves are not captured in this process; instead, a portion of their kinetic energy is converted into electricity. The cells require no light whatsoever. They transform a segment of the nonvisible spectrum into energy 365 days a year, 24 hours a day, and at any point on the Earth’s surface
Q.83 What is neutrino energy?
Answer. Neutrinos are not the easiest particles to work with. … However, certain particles, such as kaons, produce “standard candle” neutrinos that have a fixed energy. Kaons decay about 64% of the time into a muon and a muon neutrino, and if the kaon is at rest, then the neutrino will always have an energy of 236 MeV.
Q.84 Do neutrinos have energy?
Answer. Neutrinos from nuclear reactors have a million times more energy than Big Bang neutrinos, so they can be seen by measuring their interactions with atoms. … The neutrons can be captured by certain particles that then decay and produce photons, particles of light, which can signal that a neutrino was there.
Q.85 Are neutrinos dark matter?
Answer. Cosmologists have long considered neutrinos as possible dark matter particles. However, because of their small mass (less than about 1 eV), conventional neutrinos are too fast, or “hot,” to form the dense dark matter structures needed to hold galaxies and galaxy clusters together.
Q.86 Do neutrinos pass through humans?
Answer. They come straight through the earth at nearly the speed of light, all the time, day and night, in enormous numbers. About 100 trillion neutrinos pass through our bodies every second. The problem for physicists is that neutrinos are impossible to see and difficult to detect.
Q.87 Do neutrinos exist?
Answer. A neutrino is a subatomic particle that is very similar to an electron, but has no electrical charge and a very small mass, which might even be zero. Neutrinos are one of the most abundant particles in the universe. Because they have very little interaction with matter, however, they are incredibly difficult to detect.
Q.88 Do anti neutrinos exist?
Answer. In part, it’s because certain properties of the neutral neutrinos can‘t be reversed. The electron has a negative charge (-1), so its antimatter particle, the positron, has a positive charge (+1). But neutrinos have a charge of zero—and the opposite charge of zero is still zero.
Q.89 Are neutrinos matter?
Answer. Ghost particles, they’re often called. … Particle physicists originally believed that neutrinos were massless. But in the 1990s, a team of Japanese scientists discovered that they actually have a smidgen of mass. This tiny bit of mass may explain why the universe is made up of matter, not antimatter.
Q.90 What is a neutrino particle?
Answer. A neutrino is a very small piece of matter. It’s so small that is wasn’t even discovered until 1956. There are three ‘flavors’ of neutrinos: electron, muon and tau. Most people are familiar with three particles of matter: electron, neutron and proton.
Q.91 Who coined the word neutrino?
Answer. Enrico Fermi
“The name neutrino was coined by Enrico Fermi as a word play on neutron, the Italian name of the neutron.”
Q.92 How are nuclear isomers made?
Answer. Metastable isomers can be produced through nuclear fusion or other nuclear reactions. A nucleus produced this way generally starts its existence in an excited state that relaxes through the emission of one or more gamma rays or conversion electrons.
Q.93 What is isomeric transition?
Answer. An isomeric transition is a nuclear process in which a nucleus with excess energy following the emission of an alpha particle or a beta particle emits energy without changing its number of protons or neutrons.
Q.94 What is nuclear transition?
Answer. Nuclear transitions are between energy levels in the nucleus. Types of nuclear transitions lead to the emission of alpha, beta, or gamma radiation. Atomic transitions involve changes in the electron orbitals. These changes can be the emission of X-Rays from chances involving the innermost electron shells of the atom.
Q.95 What is meant by nuclear isomerism?
Answer. Also called nuclear isomerism. Physics. the relation of two or more nuclides that have the same atomic number and mass number but different energy levels and half-lives.
Q.96 Why chain isomerism is called nuclear isomerism?
Answer. Nuclear isomers are atoms with the same mass number and atomic number, but with different states of excitation in the atomic nucleus. The higher or more excited state is called a metastable state, while the stable, unexcited state is called the ground state
Q.97 What are isomers examples?
Answer. Butane and isobutane have the same number of carbon (C) atoms and hydrogen (H) atoms, so their molecular formulas are the same. However, each one has a different structural formula, which shows how the atoms are arranged. So we can say that butane and isobutane are structural isomers.
Q.98 What are the three types of isomers?
Answer. There are two broad types of isomers: constitutional and stereoisomers. Constitutional isomers differ in bonding and connectivity. Stereoisomers differ in 3D orientation. Enantiomers and diastereomers are two sub-types of stereoisomers.
Q.99 Why stable nuclei have more neutron than protons?
Answer. For stable nuclides having atomic number Z<20, the number of neutrons is equal to the number of protons, For Z>20, the number of neutrons has to be greater than number of protons for stability of the nucleus. This is because for stable nuclei having large values of Z, the coulomb force of repulsion between the protons becomes very large. In order to compensate for this large repulsive force there has to be greater number of neutrons. This is why stable nuclei have more neutrons than protons.
Q.100 What is the basic point of difference between the liquid drop model and shell model of the nucleus?
Answer. In liquid drop model of the nucleus, it is assumed that the nucleons exert an influence on one another only at close range i.e., they interact strongly only with their immediate neighbors.
The shell model treats the nucleons individually and it is assumed that the nucleons do not, at all interact with each other.
Q.101 The nucleus 2He4 has no magnetic moment. Explain.
Answer. The nucleus 2He4 contains two protons and neutrons, so that the first shell is completely filled up and l=0 . The neutrons and protons with opposing spin pair off and their magnet moments cancel each other. This is why 2He4 nucleus has no magnetic moment.
Q.102 Consider the statement, “each nucleon in a nucleus interacts chiefly with the general force field produced by all other nucleons”. This statement refers to which model?
Answer. In the shell model of nucleus each nucleon in a nucleus interacts chiefly with a general force field produced by all other nucleons.
Q.103 Consider the statement, each nucleon in a nucleus interacts only with its nearest neighbors and represents two different models of the nucleus”. This statement refers to which model?
Answer. In liquid drop model each nucleon in a nucleus interacts only with nearest neighbors.
Q.104 Discuss briefly the chief experimental systematic which led to the shell model description for nuclear states.
Answer. The main experimental evidence in support of the nuclear shell model is the existence of magic numbers. When the number of the neutrons or of the protons in a nucleus is 2, 8, 20, 28, 50, 82, and 126, the nucleus is very stable. In nature the abundance of nuclides with such magic numbers are larger than those of the nearby numbers. Among all the stable nuclides, those of neutron numbers 20, 28, 50 and 82 have more isotones, those of proton numbers 8, 20,28,50,82 have stable isotopes, than the nearby nuclides. The existence of such magic numbers implies the existence of shell structure inside a nucleus similar to the electron energy levels in an atom.
Q.105 Explain the statement that, “All the even-even nuclei have 0+ ground state”.
Answer. According to the nuclear shell model, the protons and the neutrons in an even-even nucleus tend to pair off separately i.e. each pair of neutrons or protons are in the same orbit and the opposite spins, so that the angular momentum and the total spin of each pair of nucleons are zero. It follows that the total angular momentum of the nucleus is zero. The parity of each pair of nucleons is (-1)2l =+1, and so the total parity of the system is even. Hence even-even nuclei have 0+ ground state.
Q.106 The motion of individual nucleon inside a nucleus may be regarded as independent from each other even though they interact very strongly. Explain this statement on the basis of physical principles.
Answer. It was assumed that the interaction among nucleons can be replaced by the action on a nucleon of the mean field produced by the other nucleons. The nucleons are considered to move independently of one another. Despite the high nucleon density inside a nucleus it is assumed that the individual interactions between nucleons do no manifest macroscopically. Since nucleons are fermions, all the low energy levels of the ground state are filled up and the interactions among the nucleons cannot excite a nucleon to higher level. We can then employ a model of moderately weak interaction to describe the strong interactions among nucleons.
Q.107 Nuclei with outer shells partially filled by odd number of nucleons tend to have permanent deformation why?
Answer. Nucleons in the outermost partially-filled shell can be considered as moving around a nuclear system of zero spin. For nucleon with l≠0, the orbits are ellipses. Because such odd nucleons have finite spins and magnetic moments, which can polarize the nuclear system, the nucleus tends to have permanent deformation.
Q.108 In the nuclear shell model, orbital is filled in the order;
1s1/2 , 1p3/2 , 1p1/2, 1d5/2,2s1/2 , 1d3/2 etc What is responsible for the splitting between the p3/2 and p ½ orbital?
Answer. The splitting between p3/2 , and p1/2 is caused by the spin-orbit coupling of the nucleons.
