All exercise Short Questions of Elementry Particles of book Nuclear Physics for BS/MSc Physics students.
Q.1 What do you mean by elementary particles?
Answer. Any of the particles of which matter and energy are composed or which mediate the fundamental forces of nature; especially: one (as the photon or the electron) whose existence has not been attributed to the combination of other more fundamental entities.
Q.2 What is an elementary particle made of?
Answer. Of the particles that make up an atom, only the electron is an elementary particle. Protons and neutrons are made of quarks, which makes them composite particles, particles that are made of other particles. There are three basic properties that describe an elementary particle: ‘mass’, ‘charge’, and ‘spin’.
Q.3 What are the 12 elementary particles?
Answer. The 12 elementary particles of matter are six quarks (up, charm, top, Down, Strange, Bottom) 3 electrons (electron, muon, tau) and three neutrinos (e, muon, tau). Four of these elementary particles would suffice in principle to build the world around us: the up and down quarks, the electron and the electron neutrino.
Q.4 What is a particle kid friendly definition?
Answer. This is an atom, and it is very small. Atoms are made up of particles. Red circles represent protons and blue circles represent neutrons. … Particles are tiny bits of matter that make up everything in the universe. In particle physics, an elementary particle is a particle which cannot be split up into smaller pieces.
Q.5 Which particle in an atom is an elementary particle?
Answer. Atoms are constructed of two types of elementary particles: electrons and quarks. Electrons occupy a space that surrounds an atom’s nucleus. Each electron has an electrical charge of -1. Quarks make up protons and neutrons, which, in turn, make up an atom’s nucleus.
Q.6 How are elementary particles classified?
Answer. The fundamental particles may be classified into groups in several ways. First, all particles are classified into fermions, which obey Fermi-Dirac statistics and bosons, which obey Bose-Einstein statistics. … There are also three particles, the W+, W−and Z0 bosons, which are spin 1.
Q.7 What is the smallest elementary particle?
Answer. Today, we know that atoms do not represent the smallest unit of matter. Particles called quarks and leptons seem to be the fundamental building blocks – but perhaps there is something even smaller. Physicists are still far from understanding why a proton has about 2,000 times more mass than an electron.
Q.8 Why do elementary particles exist?
Answer. Elementary particles. Electrons and quarks contain no discernible structure; they cannot be reduced or separated into smaller components. … Neutrinos do not exist within atoms in the sense that electrons do, but they play a crucial role in certain types of radioactive decay.
Q.9 How many types of elementary particles are there?
Answer. The Standard Model currently accounts for 6 quarks (up, down, strange, charm, bottom, top), 6 antiquarks, 6 leptons (electron, muon and tau, and their respective neutrinos), 6 antileptons, 13-gauge bosons (8 gluons, photon, W+, W-, Z and graviton) and 1 Higgs boson. That adds up to 38 distinct elementary particles.
Q.10 Is a photon an elementary particle?
Answer. The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles). … The quanta in a light wave are not spatially localized.
Q.11 Are protons and neutrons elementary particles?
Answer. Protons and neutrons are not fundamental particles: they are composed of quarks and gluons. Electrons are fundamental because they cannot be divided further and other particles of the same kind decay into electrons or are electron antiparticles. There are many other particles considered fundamental in particle physics.
Q.12 What is the difference between fundamental particles and elementary particles?
Answer. Atoms are Elementary Particles. A particle that has no components can be said to be Fundamental. … Electrons are elementary particles but they are sub-atomic particles. Protons and Neutrons are not elementary particles.
Q.13 What is a boson particle?
Answer.. In quantum mechanics, a boson (/ˈboson/, /ˈboson/) is a particle that follows Bose–Einstein statistics. Bosons make up one of the two classes of particles, the other being fermions. … This property holds for all particles with integer spin (s = 0, 1, 2, etc.) as a consequence of the spin–statistics theorem.
Q.14 Are hadrons elementary particles?
Answer. Hadrons. Hadrons are subject to the strong nuclear force, they are not fundamental particles as they are made up of quarks.
Q.15 How many elementary particles are there in the universe?
Answer. 1086 elementary particles
The number of protons in the observable universe is called the Eddington number. In terms of number of particles, some estimates imply that nearly all the matter, excluding dark matter, occurs in neutrinos, and that roughly 1086 elementary particles of matter exist in the visible universe, mostly neutrinos.
Q.16 How many different particles are there?
Answer. There are, in principle, an infinite number. There are the particles that we have observed in Nature – the three types of electrons and three types of neutrinos, six quarks, various gluons, the photon, two W bosons, the Z boson and the Higgs boson. There are anti-particles of many of these.
Q.17 What is the tiniest thing in the universe?
Answer. Then the atom was discovered, and it was thought indivisible, until it was split to reveal protons, neutrons and electrons inside. These too, seemed like fundamental particles, before scientists discovered that protons and neutrons are made of three quarks each.
Q.18 What’s inside a quark?
Answer. Inside the Quark. … They’ve found that an atom has a nucleus, that a nucleus contains protons and neutrons, and that those particles in turn are made of quarks and gluons–particles that bind quarks together. But most physicists believe quarks to be the smallest building blocks of matter.
Q.19 Are particles just waves?
Answer. Wave–particle duality is the concept in quantum mechanics that every particle or quantum entity may be partly described in terms not only of particles, but also of waves. … For macroscopic particles, because of their extremely short wavelengths, wave properties usually cannot be detected.
Q.20 Who discovered elementary particles?
Answer. The Discovery of Elementary Particles
The first subatomic particle to be discovered was the electron, identified in 1897 by J. J. Thomson. After the nucleus of the atom was discovered in 1911 by Ernest Rutherford, the nucleus of ordinary hydrogen was recognized to be a single proton. In 1932 the neutron was discovered.
Q.21 What are the properties of elementary particles?
Answer. There are four fundamental forces in the Universe:
gravitation (between particles with mass)
electromagnetic (between particles with charge/magnetism)
strong nuclear force (between quarks)
weak nuclear force (operates between neutrinos and electrons)
Q.22 What’s smaller than a quark?
Answer. A quark is a fundamental particle that is smaller than any measuring instrument we currently have but does that mean there’s nothing smaller? Following the discovery of quarks inside protons and neutrons in the early 1970s, some theorists suggested quarks might themselves contain particles known as ‘prions’
Q,23 Where would u find a quark?
Answer. Due to a phenomenon known as color confinement, quarks are never directly observed or found in isolation; they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons.
Q.24 What is the Higgs boson particle in simple terms?
Answer. Bosons are thought to be particles which are responsible for all physical forces. Other known bosons are the photon, the W and Z bosons, and the gluon. Scientists do not yet know how to combine gravity with the Standard Model. The Higgs field is a fundamental field of crucial importance to particle physics theory.
Q.25 Why is it called the God particle?
Answer. The Higgs boson particle is so important to the Standard Model because it signals the existence of the Higgs field, an invisible energy field present throughout the universe that imbues other particles with mass. Since its discovery two years ago, the particle has been making waves in the physics community.
Q.26 What is God particle theory?
Answer. In 2012, scientists confirmed the detection of the long-sought Higgs boson, also known by its nickname the “God particle,” at the Large Hadron Collider (LHC), the most powerful particle accelerator on the planet. This particle helps give mass to all elementary particles that have mass, such as electrons and protons.
Q.27 What is a lepton particle?
Answer. In particle physics, a lepton is an elementary particle of half-integer spin (spin 1⁄2) that does not undergo strong interactions. Two main classes of leptons exist: charged leptons (also known as the electron-like leptons), and neutral leptons (better known as neutrinos).
Q.28 What are the 17 particles of the standard model?
Answer. The Standard Model describes approximately 200 particles and their interactions using 17 fundamental particles, all of which are fermions or bosons: 6 quarks (fermions), 6 leptons (fermions), 4 force-carrying particles (gauge bosons), and the Higgs boson.
Q. 28 What is the smallest thing we can see with our eyes?
As the image sent to the eye by way of the lens increases, you see an object more easily, even though its physical size has not changed. Experts believe that the naked eye — a normal eye with regular vision and unaided by any other tools — can see objects as small as about 0.1 millimeters.
Q.29 What creates a photon?
Answer. A photon is produced whenever an electron in a higher-than-normal orbit falls back to its normal orbit. During the fall from high energy to normal energy, the electron emits a photon — a packet of energy — with very specific characteristics.
Q.30 What is a pion made of?
Answer. Pions (commonly shortened to a π) are a type of meson, which are subatomic particles made of a combination of quarks and antiquarks. Since antiquarks are antimatter, they will annihilate the same type (known as a flavour) of quark if they come near it.
Q.31 Are Pions strange?
Answer. Pions are not produced in radioactive decay, but commonly are in high energy collisions between hadrons. … The Pions, which turned out to be examples of Yukawa’s proposed mesons, were discovered later: the charged Pions in 1947, and the neutral pion in 1950.
Q.32 What is pi meson theory?
Answer. In 1935 Japanese scientist H.Yukawa explained the mechanism of interaction of the elementary particles(Neutrons & Protons) in a nucleus. In order to explain his theory he considered a particle known as Pions/mesons(π°) and that came to be known as Meson theory. A pion has two sub particles such as π- & π+.
Q.33 What are Pions and kaons?
Answer. EXOTIC subatomic particles, such as Pions, kaons and hyperons, are produced constantly in the Earth’s atmosphere. Cosmic rays – high-energy particles (mainly protons) from outer space – bombard atoms in the upper atmosphere, causing spectacular nuclear disintegrations
Q.34 How are Pions created?
Answer. Pions are particles which consists of a quark and an anti quark. They can be formed, whenever there are the corresponding quarks and enough energy available. For example, they can be formed by colliding protons head-on at the LHC at Cern.
Q.35 Is a pion a boson?
Answer. The proton is a spin 1/2 particle (fermion), the Pions are spin 0 particles (bosons). The orbital angular momentum quantum number can only be an integer, so there is no way that angular momentum can be conserved. The proposed decay cannot occur.
Q.36 Does a Pions have strangeness?
Answer. It is a property of subatomic particles, and only applies to those known as hadrons, which include protons, neutrons, Pions, kaons, and lambda, omega, and rho particles, among others. The symbol for strangeness is Of the six flavors of quarks, only the strange quark has a nonzero strangeness.
Q.37 What are the six quarks?
Answer. There are six types, known as flavors, of quarks: up, down, strange, charm, bottom, and top. Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state.
Q.38 What is a meson particle?
Answer. Meson, any member of a family of subatomic particles composed of a quark and an antiquark. Mesons are sensitive to the strong force, the fundamental interaction that binds the components of the nucleus by governing the behavior of their constituent quarks.
Q.39 How many types of mesons are there?
Answer. Mesons. Mesons are intermediate mass particles which are made up of a quark-antiquark pair. Three quark combinations are called baryons. Mesons are bosons, while the baryons are fermions.
Q.40 Is pion a meson?
Answer. The pion is a meson. The π+ is considered to be made up of an up and an anti-down quark.
Q.41 What is an antiquark?
Answer. The baryons and mesons are complex subatomic particles built from more-elementary objects, the quarks. Six types of quark, together with their corresponding antiquarks, are necessary to account for all the known hadrons.
Q.42 What is an antineutrino?
Answer. The antineutrino is an elementary subatomic particle with infinitesimal mass (less than 0.3eV…?) and with no electric charge. Neutrinos and antineutrinos belong to the family of leptons, which means they do not interact via strong nuclear force. …Antineutrinos are produced in the negative beta decay.
Q.43 Is a muon a lepton?
Answer. The muon is a lepton which decays to form an electron or positron. The fact that the above decay is a three-particle decay is an example of the conservation of lepton number; there must be one electron neutrino and one muon neutrino or antineutrino in the decay. The lifetime of the muon is 2.20 microseconds
Q.44 How do Pion’s decay?
Answer. Since the charged Pions decay into two particles, a muon and a muon neutrino or antineutrino, then conservation of momentum and energy give the decay products definite energies. This contrasts with the three-particle decay of the neutral pion in which the emitted particles have a range of energies and momenta.
Q.45 How are mesons formed?
Answer. They are part of the hadron particle family – particles made of quarks. The other members of the hadron family are the baryons – subatomic particles composed of three quarks. The main difference between mesons and baryons is that mesons have integer spin (thus are bosons) while baryons are fermions (half-integer spin).
Q.46 Where do mesons come from?
Answer. Because mesons are made of one quark and one antiquark, they can be found in triplet and singlet spin states.
Q.47 What is the boson for the strong force?
Answer. Gauge bosons in the Standard Model
The Standard Model of particle physics recognizes four kinds of gauge bosons: photons, which carry the electromagnetic interaction; W and Z bosons, which carry the weak interaction; and gluons, which carry the strong interaction.
Q.48 What is the strangeness of a kaon?
Answer. Kaons are mesons formed by a strange (or anti-strange) quark and an up or down quark. They have strangeness of ± 1. … In 1964, Cronin and Fitch observed that CP is not conserved in weak interaction in their experiment of a decay of a long lived neutral kaon to 2 π .
Q.49 Is strangeness conserved in strong interactions?
Answer. Baryon number is conserved in all interactions. … Strangeness is conserved in all but the weak interaction (this is because the weak interaction involves one type of quark changing into another as we have seen).
Q.50 Is a kaon a baryon?
Answer. A particle made up of an anti-quark and a quark is called a meson, and you should know that all mesons have a baryon number of 0.The antiparticle of the positive Kaon is the K- meson.
Q.51 Is a photon a lepton?
Answer. The photon is a gauge boson carrying the electromagnetic force. It can share quantum states meaning that it isn’t restricted to obeying the Pauli exclusion principle. This implies that it is indeed not a lepton, since leptons can’t share quantum states.
Q.52 How is baryon number calculated?
Answer. Baryon number. A quantum number equal to the number of baryons in a system of subatomic particles minus the number of antibaryons. Baryons have a baryon number of +1, while antibaryons have a baryon number of -1. Quarks and antiquarks have baryon numbers of +13 and -13, respectively (baryons consists of three quarks).
Q.53 What is an example of the strong nuclear force?
Answer. The most common examples are atomic nuclei. The protons in a nucleus repel each other, but the strong nuclear force binds them together.
Q.54 What type of particle is a kaon?
Answer. In particle physics, a kaon /ˈkeɪ. ɒn/, also called a K meson and denoted. , is any of a group of four mesons distinguished by a quantum number called strangeness. In the quark model they are understood to be bound states of a strange quark (or antiquark) and an up or down antiquark (or quark).
Q.55 What are lepton and baryon numbers?
Answer. The lepton family includes the electron, muon, tau, and their neutrinos. Quarks come in six types, called flavors, denoted by up (u), down (d), strange (s), charmed (c), bottom (b), and top (t) quarks. All interactions conserve the lepton numbers and the number of baryons (B).
Q.56 What is a hadron particle?
Answer. In particle physics, a hadron /ˈhadron/ ( listen) (Greek: ἁδρός, hadrons; “stout, thick”) is a composite particle made of two or more quarks held together by the strong force in a similar way as molecules are held together by the electromagnetic force.
Q.57 Why strange particles are called Strange?
Answer. No-one knew why it lived for so long so they called this property “strangeness” and the name stuck! The particle was found to be made up of three quarks: an up, a down and an extra one – which got its name from the strangeness property – the strange quark.
Q.58 What force produces strange particles?
Answer. The muon as a particle that decays into an electron. Strange particles are produced through the strong interaction and decay through the weak interaction (e.g. kaons) Strangeness as a quantum number to reflect the fact that strange particles are always created in pairs.
Q.59 Why elementary particles are called so?
Answer. Elementary particles are the smallest known building blocks of the universe. They are thought to have no internal structure, meaning that researchers think about them as zero-dimensional points that take up no space.
Q.60 Which was the first particle discovered which is still today believed to be elementary, i.e. not made up of further constituents?
Answer. Electron is a first particle that discovered first and it is also consider now as an elementary particle.
Q.61 Which elementary particle has no charge?
Answer. The fundamental particle which has no charge and has a mass almost equal to that of the positively charged fundamental particle is the neutron.
Q.62 What does strangeness mean in physics?
Answer. Strangeness (S) is a quantum number assigned to particles. The term strangeness was established before the discovery of quarks to explain differing rates of reaction when strange particles were produced and when they decayed.
Q.63 How do you find the strangeness of a particle?
Answer. We can find the strangeness of a particle by using the law of conservation of strangeness. For example, in a reaction where a negatively-charged pion interacts with a proton, a neutral kaon and a neutral lambda particle are formed.
Q.64 why the neutrino affected by electromagnetic forces?
Answer. Neutrinos do not carry electric charge. Therefore, they are not affected by the electromagnetic forces that act on charged particles such as electrons and protons.
Q.65 What are the Characteristics of Pions?
Answer. The spin of the charged Pions and neutral pi-on is found to be zero. And the intrinsic parity of pi-mesons is odd.
Q.66 What is the building block of beauty quark?
Answer. The epsilon particle that are made up of this type of quark which having charge -1/3, also known as bottom or b quark.
Q.67 Is strangeness conserved in all type of interaction?
Answer. Strangeness is conserved during the strong and the electromagnetic interaction, but not during the weak interaction because of isospin symmetry which is relate with strong interaction.
Q.68 How the mass of Pions is determined?
Answer. The Pions are produced by hitting a suitable target with a beam of high energy proton or alpha particles obtained from the accelerator. The Pions extracted from the accelerator are detected by emulsion plates. From their radius of curvature in the magnetic field of accelerator, their momenta are determined. Their ranges in nuclear emulsion plate give their kinetic energies. From these quantities the mass of Pions determined.
Q.69 What prevents the common elements heavier than iron but lighter than lead from fission spontaneously?
Answer. Although elements heavier than iron but lighter than lead can release energy in fission if we consider specific binding energies alone, the coulomb barriers prevent them from fission spontaneously. This is because the fission barriers of these nuclei are so high that the probability of penetration is very small.
Q.70 Differentiate between controlled and uncontrolled chain reaction?
Answer. Difference between controlled and uncontrolled chain reaction is given below;
| Controlled Chain reaction | Uncontrolled chain reaction |
| It is possible to produce such condition in which only one neutron out of three becomes the cause of further fission reaction. The other neutron either escape out or are absorbed in any other medium except uranium. In this case the fission chain reaction proceeds with its initial speed, this type of reaction is called controlled fission chain reaction. | We have definite amount of 92U235 and a slow neutron produces fission reaction in one atom of uranium. During this fission, three neutrons are produced. If conditions are appropriate, these neutrons will produce fission in some more atoms of uranium and more neutrons will be emitted and process repeats again and again. |
Q.71 What are the uses of nuclear reactor?
Answer. Nuclear reactors are used for the following purposes;
- Research
- Production of plutonium which is used in atomic bombs as a fuel.
- For obtaining useful energy for producing electrical and mechanical energy.
- It is used for the production of atomic energy for industrial and peaceful purposes.
Q.72 In heavy nuclei the number of protons is considerably less than the number of neutrons. Explain.
Answer. For heavy nuclei, the many protons in the nucleus cause greater coulomb repulsion. To form a stable nucleus, extra neutrons are needed to counter the coulomb repulsion. This competes with a proton-neutron symmetry effect and causes the neutron-proton ratio in stable nuclei to increase with A. Hence the number of protons in heavy nuclei is considerably less than that of neutrons.
Q.73 Why is a moderator necessary? Are light or heavy elements preferred for moderators and why?
Answer. For reactors using 92U235 fission is caused mainly by thermal neutrons. However, fission reaction emits fast neutrons: so some is moderator needed to reduce the speed of the neutrons. Lighter nuclei are more suitable as moderator because the energy lost by a neutron per neutron-nucleus collision is larger if the nucleus is lighter.
Q.74 What factors make a fusion reaction difficult to achieve?
Answer. This reaction required large amount of energyand temperature up to million degrees centigrade. So these requirements are not possible to achieve so the fusion reaction is very difficult to achieve.
Q.75 State the advantages and disadvantages of fusion power from the point of safety pollution and resources.
Answer. Advantages;
- The fusion reaction is free from radioactive products so it will be safe from pollution and resources.
- This reaction produces more energy per nucleon.
- The energy produced by fusion is cheaper than the fission process
Disadvantages;
- It is more difficult to start the fusion reaction.
- Fusion reaction has not been brought under control like fission reaction. Thus, it can be used to produce electricity.
Q.76 Which of the radiations would you advise and why for?
- Treatment of the skin of a patient.
- Treatment of flesh just under skin
- Treatment of infection in the interior of the body
Answer. Alpha particle should be advised to treat the skin due to their very small penetrating power.
- Beta particles should be advised for treatment of flesh under the skin because they have comparatively greater penetration power than alpha particles.
- Gamma rays should be advised for the treatment of an infection in the interior of the body because they have largest penetration power.
Q.77 What do you mean by critical mass and critical volume?
Answer. Critical mass;
Such a mass of uranium in which one neutron out of all the neutrons produced in one fission reaction produces further fission is called critical mass.
Critical Volume;
The volume of the critical mass is called critical volume.
Q.78 Explain, why neutron activated nuclides tend to decay by β– rather than β+?
Answer. As in neutron activated nuclides, the number of neutrons increases. Therefore, in order to obtain stability, nucleus converts the neutron into proton by emission of β– . Thus as neutron activate nuclides containing more neutrons, so they tend to decay by β– rather than β+.
