All exercise Short Questions of Nature of Nuclear Forces of Nucleus of book Nuclear Physics for BS/MSc Physics students.
Q. No.1 What is nuclear force in physics?
Ans. Nuclear forces (also known as nuclear interactions or strong forces) are the forcesthat act between two or more nucleons. They bind protons and neutrons (“nucleons”) into atomic nuclei. The nuclear force is about 10 millions times stronger than the chemical binding that holds atoms together in molecules.
Q. No. 2 What is nuclear force example?
Ans. Examples: The most obvious example of Nuclear Force, as discussed earlier, is the binding of protons, which are repulsive in nature because of their positive charge.
Q. No. 3 What is the definition of strong nuclear force?
Ans. The Strong Nuclear Force (also referred to as the strong force) is one of the four basic forces in nature (the others being gravity, the electromagnetic force, and the weak nuclear force). As its name implies, it is the strongest of the four.
Q. No. 4 What is the cause of nuclear force?
The nuclear force is caused by the exchange of pions. At a more fundamental level the nuclear force becomes the strong force, caused by the exchange of gluons. The strong force acts between the quarks inside the nucleons. … The gluons “glue” quarks into protons, neutrons, and pions.
Q. No. 5 What are the two nuclear forces?
The Nuclear Force. The nuclear force acts between all of the particles in the nucleus, i.e., between two neutrons, between two protons, and between a neutron and a proton. It is attractive in all cases. In contrast, an electrical force acts only between two protons and it is repulsive.
Q. No. 6 What is the strongest force on earth?
S. Nicole. Out of these four, the weakest one is gravity and the strongestfundamental force is the strong nuclear force; it is 100 times stronger than the electromagnetic force.
Q. No. 7 What are examples of weak nuclear force?
Beta decay is just one example of the weak force. During beta decay a neutron disappears and is replaced by a proton, an electron and a neutrino (anti-electron). It is also proven that a down quark disappears and an up quark is produced.
Q. No. 8 Which is the strongest force in nature?
Why is gravity the strongest force? Actually, gravity is the weakest of the four fundamental forces. Ordered from strongest to weakest, the forces are 1) thestrong nuclear force, 2) the electromagnetic force, 3) the weak nuclear force, and 4) gravity.
Q. No. 9 Is the weak nuclear force attractive?
While the other forces hold things together, the weak force plays a greater role in things falling apart, or decaying. The weak force, or weak interaction, is stronger than gravity, but it is only effective at very short distances.
Q. No. 10 What is the difference between weak and strong nuclear force?
The Strong Nuclear Force is an attractive force between protons and neutrons that keep the nucleus together and the Weak Nuclear Force is responsible for the radioactive decay of certain nuclei. It was realized that the strength of the two forcesdiffered a lot.
Q. No. 11 Why is there a strong nuclear force?
It seemed that they would do so due to the repulsive electromagnetic force betweenthe positively charged protons located in the nucleus. It was later found that the strong force not only holds nuclei together, but is also responsible for binding together the quarks that make up hadrons.
Q. No. 12 What are the four forces?
The Four Fundamental Forces of Nature
- The Four Fundamental Forces and their strengths. Gravitational Force – Weakest force; but infinite range. ( …
- Gravitational Force. …
- Weak Nuclear Force. …
- Electromagnetic Force. …
- Strong Nuclear Force. …
- Electroweak Theory and Grand Unification Theories (GUT) …
- UPSC Prelims Question 2013.
Q. No. 13 What is the nature of nuclear force?
Answer is Nuclear force which are attractive in nature and strong enough to overcome the electrostatic force of repulsion between two protons. So it is thenuclear forces which holds neutrons and protons (nucleons) together to form a nucleus. Nucleus forces are complex in nature and difficult to understand.
Q. No. 14 What would happen if there was no strong nuclear force?
What if there was no strong force, what would happen? The Strong Nuclear Force is responsible for the binding of protons and neutrons to form atomic nuclei. … Atoms would be impossible because the Quarks wouldn’t bind with each other to form Protons and Neutrons.
Q. No. 15 What are the characteristics of nuclear force?
Answer: The two characteristic properties of nuclear force: Nuclear forces are independent of the charge of protons and neutrons. … It depends on the spins of the nucleons that is whether they are parallel or no and also on the non central or tensor component of nucleons.
Q. No. 16 Why nuclear force is short range?
The term itself says that it is a force of very short range as the term is “NuclearStrong Force“, it is the force that exists in nucleus which binds the protons and the neutrons together, in the absence of this force the protons would repel each other and blow the nucleus apart.
Q. No. 17 Is the strong nuclear force always attractive?
The nuclear force is always attractive, the electromagnetic always repulsive in the nucleus. The distance comes in because the closer charged nucleons approach, the largest the repulsion, the strongest the attraction, the balance depends on the strengths and the distance.
Q. No.18 How do we know strong nuclear force exists?
So a clearly there must be a force “The Strong Force” or “Nuclear Force” that overcome this repulsion and keeps the nucleus together. This Force is created by the exchange of particles called mesons. As we all know, protons are located in the nucleus of the atom. All of them are positively charged.
Q. No. 19 What is the most powerful thing in the universe?
That’s about the same amount of energy in 10 trillion trillion billion megaton bombs! These explosions generate beams of high-energy radiation, called gamma-ray bursts (GRBs), which are considered by astronomers to be the most powerful thing in the universe.
Q. No. 20 Where is weak nuclear force found?
In particle physics, the weak interaction, which is also often called the weak force orweak nuclear force, is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms.
Q. No. 21 What is the order of weak nuclear force?
The Weak Force
One of the four fundamental forces, the weak interaction involves the exchange of the intermediate vector bosons, the W and the Z. Since the mass of these particles is on the order of 80 GeV, the uncertainty principle dictates a range of about 10-18meters which is about 0.1% of the diameter of a proton.
Q. No. 22 Who discovered electrostatic force?
1780s Coulomb and his torsion balance, proving the electric force is inverse square over a distance, and finding k coulomb’s constant.
Q. No. 23 Who is the father of electrostatics?
The father of electrostatics is Thales of Miletus.
Q. No 24 Who discovered electromagnetic force?
The discovery of electromagnetic induction was made almost simultaneously, although independently, by Michael Faraday, who was first to make the discovery in 1831, and Joseph Henry in 1832.
Q. No. 25 Who discovered Gravitational force?
Sir Isaac Newton was an English mathematician and mathematician and physicist who lived from 1642-1727. The legend is that Newton discovered Gravity when he saw a falling apple while thinking about the forces of nature.
Q. No. 26 What is the origin of gravitational force?
Gravity is most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915) which describes gravity not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass.
Q. No 27 Who discovered the nuclear force?
Hideki Yukawa
Therefore, the concept of a new strong nuclear force was introduced. In 1935, the first theory for this new force was developed by the Japanese physicist Hideki Yukawa (Yukawa,1935), who suggested that the nucleons would exchange particles between each other and this mechanism would create the force.
Q.28 It is said that nuclear forces are short range force. Give evidence in support of this statement.
Answer: It is well known fact that nuclear forces are short range forces, if these are long range forces, then each nucleon will come under the influence of all other nucleons in the nucleus. In such a case , the binding energy will be proportional to A2 (the square of the number of the nucleons in the nucleus). But experimentally the binding energy per nucleon if these are short range forces, then each nucleon will come under the influence of only those nucleons which are in its immediate vicinity in the nucleus and these alone will contribute to the binding energy of the nucleons making it almost proportional to the A.
2.29 Why π- mesons are called virtual mesons?
Answer: The π- mesons remain free for an extremely short time (less than 10-23 sec) and are undetectable. In this small time they violate the energy conservation laws. Due to this reason these mesons are called virtual mesons.
2.30 What are the properties that identify a system of nucleons in its lowest energy state? Discuss the non- classical properties.
Answer: The ground state of the system of nucleons is identified by its spin, parity and isospin quantum numbers. Spin and parity are determined by those of the last one or two unpaired nucleons. For the ground state of an even – even nucleus, Jp=0+. For an even –odd nucleus, the nuclear spin and parity are determined by the last nucleons. The isospin of the nuclear ground state is;
$$\mathbf{I=\frac{1}{2} |N-Z|}$$
2.31 If the nuclear force is charge independent and a neutron and a proton from a bound state, then why is there no bound state for two neutrons? What information does this provide on the nucleon-nucleon force?
Answer: A system of a neutron and a proton can form either singlet or triplet spin state. The bound state is the triplet state because the energy level of the singlet state is higher. A system of two neutrons which are in the same energy level can form only singlet spin state, and no bound state is possible. This shows the spin dependency of the nuclear force.
2.32 A proton and a neutron can undergo radioactive capture at rest according to the reaction; $\mathbf{P + n \rightarrow d + \gamma\ }$ . Find the energy of the photon emitted in this capture.
Answer
The energy released in the radioactive capture is,
E= (m n +mp-m d ) c2 = (1.00867+1.00783-2.01410) X 931 MeV
This energy appears as the kinetic energies of the photon and recoil deuteron.
2.33 Is the binding energy of the nuclei more nearly proportional to A=(N+Z) or to A2 ?
Answer
The nuclear binding energy is more proportional to A with a coefficient of 15.6 MeV . Because of the saturation property of nuclear forces, a neutron can only interact with its immediate neighbors and hence with only a limited number of other nucleons. For this reason the binding energy is proportional to A, rather than to A2, which would be the case if the nucleon interacts with all nucleons in the nucleus. Nuclear forces are therefore short- range forces.
2.34 The deuteron is a bound state of a proton and a neutron of total angular momentum J=1. It is known to be principally a S(l=0) state with a small admixture of a D (l=2) state. Explain why a P state cannot contribute?
Answer
The P state has parity opposite to that of S and D states. As parity is conserved in strong interactions state of opposite parities cannot be mixed. Hence the P state cannot contribute to a state involving S and states.
2.35 The experimental values of magnetic moment of a free proton and free neutron support Yukawa meson field theory. Explain the statement.
Answer
A free proton is , for a part of its lifetime a neutron with a closely bound π+ -meson. Thus the net magnetic moment of a free proton will exceed that given by simple theory. Similarly a neutron is , for a fraction of its lifetime dissociated into a proton and π—meson. This combination will have magnetic moment. It, therefore, follows that a neutron though uncharged will have a magnetic moment as predicted by Yukawa theory.
2.36 The deuteron has J=1 and a magnetic moment ( µd = 0.857 µN). How might one interpret the lack of exact equality µd and µp + µn ?
Answer
The difference between d and p +
n cannot be explained away by experimental errors. It is interpreted as due to the fact that the neutron and proton are not in a pure 3S1 state, but in a mixture of 3S1 and 3D1 states. If a proportion of the latter of about 4% is assumed , agreement with the experimental value can be achieved.
2.37 Show that the classical cross section for elastic scattering of particles from an infinitely massive sphere of radius R is isotropic.
Answer
In classical mechanics, in elastic scattering of a point particle from a fixed surface, the emergent angle equals the incident angle. Thus if a particle moving along the – z direction impinges on a hard sphere of radius R at a surface point of polar angle , it is denoted by an angle
= 2
. As the impact parameter is b=Rsin
, the differential scattering cross section is
$$\mathbf{\frac{d\sigma }{d\mho }= \frac{2\pi bdb}{2\ \pi sin\alpha d\alpha} = R2\frac{sin\theta cos\theta d\theta}{4sin\theta cos\theta d\theta} = R2 / 4}$$
Which is independent of θ, showing that the scattering is isotropic.
