Advance Physics MCQs – Nucleus ( Advance Physics ) MCQs
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Advance Physics MCQs – Nucleus ( Advance Physics ) MCQs
The most occurred mcqs of Nucleus ( ) in past papers. Past papers of Nucleus ( Advance Physics ) Mcqs. Past papers of Nucleus ( Advance Physics ) Mcqs . Mcqs are the necessary part of any competitive / job related exams. The Mcqs having specific numbers in any written test. It is therefore everyone have to learn / remember the related Nucleus ( Advance Physics ) Mcqs. The Important series of Nucleus ( Advance Physics ) Mcqs are given below:
Atomic Masses and Composition of Nucleus
1. The neutron was discovered by whom?
a) Marie Curie
b) Pierre Curie
c) Rutherford
d) James Chadwick
Answer: d
Explanation: Neutrons are chargeless subatomic particles. It was discovered by James Chadwick in 1932. They are present in all-atom nuclei except those of ordinary hydrogen. The neutron was initially very difficult to detect and therefore, the last to be discovered.
2. The magnetic moment of a revolving electron around the nucleus varies with the principal quantum number as which of the following?
a) μ ∝ n
b) μ ∝ 1n
c) μ ∝ n2
d) μ ∝ 1n2
Answer: a
Explanation: L = nh2π and μ = eL2m.
μ = enh2m.2π
Therefore, μ ∝ n.
3. Which of the following has the highest neutron ratio?
a) 8O16
b) 2He4
c) 26Fe56
d) 92U235
Answer: d
Explanation: The nucleus of Uranium 235(92U235) has 234 – 92 = 142 neutrons.
Therefore, It has the highest proton to neutron ratio, i.e.
= The number of protons: the number of neutrons
= 142:92
4. When a radioactive substance emits an α-particle, its position in the periodic table is lowered by which of the following?
a) One place
b) Two places
c) Three places
d) Four places
Answer: b
Explanation: When a radioactive substance emits an α-particle, its atomic number decreases by a factor of 2. Therefore, its position in the periodic table is also lowered by two places.
5. If alpha, beta, and gamma rays carry the same momentum, which has the longest wavelength?
a) Alpha rays
b) Beta rays
c) Gamma rays
d) All have the same wavelength
Answer: d
Explanation: Wavelength of de Broglie waves is given as:
λ = hp.
As momentum is the same for all rays, all have the same wavelength λ.
6. β-rays emitted from radioactive material are known as electromagnetic radiation.
a) True
b) False
Answer: b
Explanation: No, this is a false statement. β-rays are charged particles emitted by radioactive nuclei. Therefore, these rays are highly energetic electrons that are released from the inside of a nucleus. Thus, these are not electromagnetic radiations.
7. If elements with principal quantum number n > 4 were not allowed in nature, then what will be the number of possible elements?
a) 60
b) 20
c) 4
d) 64
Answer: a
Explanation: Maximum number of electrons in an orbit = 2n2.
As n > 4 is not allowed, the number of possible elements = 2(1)2 + 2(2)2 + 2(3)2
Number of possible elements = 2(4)2
Number of possible elements = 60.
8. For uranium nucleus how does its mass vary with volume?
a) m ∝ V
b) m ∝ 1V
c) m ∝ √V
d) m ∝ V2
Answer: a
Explanation: Mass of nucleus = Nuclear density × Volume.
The nuclear density of an atom is constant (10-17 kgm-3) for all nuclei, therefore, the mass of the nucleus is directly proportional to the volume.
9. Which of the following is a correct statement?
a) Beta rays are the same as for cathode rays
b) Gamma rays are high energy neutrons
c) Alpha particles are singly ionized helium atoms
d) Protons and neutrons have the same mass
Answer: a
Explanation: β-rays are electrons of nuclear origin. Therefore, they have the same nature as the cathode rays. The other statements are not valid.
10. Which is a non-central force?
a) Electrostatic force
b) Nuclear force
c) Gravitational force
d) Spring force
Answer: b
Explanation: Nuclear force is a non-central force. They are dependent on the spin of the nuclei, and not on whether the nucleons are protons or neutrons. The tensor force exists between two nucleons, and therefore, it has a tensor component.
Size of the Nucleus
1. Identify the expression for the nuclear radius from the following.
a) R = R0 ∛A
b) R = R0 √A
c) R = R0 A3
d) R = R0 A2
Answer: a
Explanation: Most of the nuclei of atoms are spherical in structure. The expression for the nuclear radius is given by:
R = R0 ∛A
Where R0 is a constant and A is the mass number. The nuclear radius is measured in Fermi meter.
1 fm = 10-15 m.
2. Who measured the size of the nucleus first?
a) Bohr
b) Einstein
c) Rutherford
d) Geiger and Marsden
Answer: c
Explanation: Rutherford was the form to measure the size of the nuclei of an atom by 1911. He discovered that these were about 104 times smaller than the atoms that constituted them and this was due to the fascinating way that the alpha particles scattered from metal foils.
3. Which of the following is a stable nucleus?
a) The nucleus with even protons and odd electrons
b) The nucleus with even number of protons and neutrons
c) The nucleus with even neutrons and odd protons
d) The nucleus with odd protons and neutrons
Answer: b
Explanation: The nuclei of atoms having even numbers of both protons and neutrons are the most stable ones and this also means that they are less radioactive than nuclides containing even numbers of protons and odd numbers of neutrons.
4. If the internal energy of a nucleus is high, then it is radioactive.
a) True
b) False
Answer: a
Explanation: Yes, this is a true statement. An atom is said to be unstable, or in other words, radioactive when the forces that it is subjected to it are unbalanced. Therefore, when there is an excess of internal energy, instability of an atom’s nucleus occurs and hence they can become radioactive. This may also result from an excess of either neutrons or protons in the nucleus.
5. A nucleus at rest splits into two nuclear parts having radii in the ratio of 1:3. Find the ratio of their velocities.
a) 1:9
b) 3:1
c) 1:27
d) 27:1
Answer: d
Explanation: Given: R1 = R0 (A1)1/3 and R2 = R0 (A2)1/3
R1R2=(A1A2)13 or A1A2=(R1R2)3=(13)3
A1A2=127
So, the ratio of their masses is given as:
m1m2=127
According to the principle of conservation of momentum, the magnitude of p1 = magnitude of p2
m1v1 = m2v2
v1v2=m2m1=271 = 27:1.
Nuclear Force
1. Which of the following best define nuclear forces?
a) The attraction between protons and neutrons
b) Repulsion between protons and neutrons
c) The attraction between protons and electrons
d) The attraction between electrons and neutrons
Answer: a
Explanation: The protons and neutrons are held together by the strong attractive forces inside the nucleus of an atom. These forces are known as nuclear forces. The other statements are not valid and do not define nuclear forces.
2. Find the true statement.
a) Nuclear charge is dependent on the charge
b) The nuclear force is weaker than the electromagnetic force
c) The nuclear force is independent of charge
d) The nuclear force is weaker than the gravitational force
Answer: c
Explanation: Nuclear force is independent of charge. The nuclear force between two protons is the same as that between two neutrons or between a neutron and proton. This is known as charge independent character of nuclear force. Also, nuclear force is stronger than the electromagnetic and gravitational force.
3. What is the energy released in a nuclear reaction called?
a) R-value
b) Q value
c) P-value
d) Nuclear energy
Answer: b
Explanation: In a nuclear reaction, the sum of masses before the reaction is greater than the sum of masses after the reaction. The difference in masses appears in the form of energy following the law of inter-conversion of mass and energy. Thus, the energy released in a nuclear reaction is called a Q value of a reaction.
4. The nuclear force is short-ranged.
a) True
b) False
Answer: a
Explanation: Yes, this is a true statement. The nuclear force exists in small regions, i.e. the diameter of 10-15 m = 1 fm. The nuclear force between two nucleons decreases rapidly as the separation between them increases and becomes negligible at separation more than 10 fm.
5. Which of the following is the main result of nuclear fission?
a) Helium
b) Strontium
c) Krypton
d) Barium
Answer: d
Explanation: The breaking of a heavy nucleus into two or more fragments of comparable masses, with the release of a tremendous amount of energy is called nuclear fission. The most typical fission reaction occurs when slow-moving neutrons strike Uranium 235 to form the main product barium. The nuclear reaction is given as:
23592U + 10n ➔ 14156Ba + 9236Kr + 310n + 200 MeV
6. Uranium 235 mass should be greater than X, then it is capable of continuous fission by itself. Identify X.
a) Critical size
b) Threshold point
c) Critical shape
d) Specific size
Answer: a
Explanation: If more than one of the neutrons produced in the fission of uranium 235 is capable of inducing a fission reaction, then the number of fissions taking place at successive stages goes increasing at a very brisk rate and this generates a series of fission reactions. This is known as a chain reaction. If the mass of the Uranium235 sample is greater than a certain size called the critical size then it is capable of continuous fission by itself. So, X is critical size.
7. Which of the following forms the basis of a nuclear reactor?
a) Uncontrolled chain reaction
b) Fast nuclear reaction
c) Controlled chain reaction
d) Catalyst controlled nuclear reaction
Answer: c
Explanation: In a chain reaction, the fast-moving neutrons are absorbed by certain substances known as moderators such as heavy water, then the number of fissions can be controlled and the chain reaction in such a case is known as a controlled chain reaction. This forms the basis of a nuclear reactor.
8. Controlled chain reactions form the basis of an atomic bomb.
a) True
b) False
Answer: b
Explanation: No, this is a false statement. Uncontrolled chain reactions form the basis of an atomic bomb. If the number of fissions in a given interval of time goes on increasing continuously, then a condition of an explosion is created, and this is known as uncontrolled chain reactions.
9. Why is a fusion reaction difficult to perform?
a) The nuclei are set up far from each other
b) The attraction between the nuclei
c) Sun’s energy is not sufficient
d) Repulsion between the nuclei
Answer: d
Explanation: For the fusion reaction to occur, the light nuclei are brought closer to each other, at a distance of about 10-14 m. This is only possible at a very high temperature to counter the repulsive force between the two nuclei. Due to this reason, the fusion reaction is difficult to perform.
10. What is the energy released in the fission of 2 kg of Uranium 235? (Given: energy per fission = 200 MeV)
a) 1.64 × 1014 J
b) 1.64 × 1015 J
c) 2.64 × 1014 J
d) 1.64 × 1020 J
Answer: a
Explanation: Given: energy per fission = 200 MeV; For Uranium 235:
The number of atoms in 235 g = 6.023 × 1023
So, the number of atoms in 2 kg of Uranium 235 = (2000235) × 6.023 × 1023
N = 5.125 × 1024
Therefore, the energy released in fission of 2 kg of Uranium 235 is:
E = 200 MeV × N × 1.6 × 10-19 J
E = 200 × 106 × 5.125 × 1024 × 1.6 × 10-19 J
E = 1.64 × 1014 J
Radioactivity
1. Radioactive material decays by simultaneous emission of two particles with respective half-lives 1620 and 810 years. The time, in years, after which one-fourth of the material remains?
a) 1080
b) 2430
c) 3240
d) 4860
Answer: a
Explanation: N = N0e-(λ1 + λ2) t.
4 = e(λ1 + λ2) t.
t = (2×1620×810)(2430) = 1080 year.
2. Which of the following substances cannot be emitted by radioactive substances during their decay?
a) Protons
b) Neutrinos
c) Helium nuclei
d) Electrons
Answer: a
Explanation: Protons are not emitted by radioactive substances during their decay. They are positively charged subatomic particles found in the atomic nucleus. The others can be emitted by radioactive substances during their decay.
3. The electron emitted in β – radiation originates from where?
a) Inner orbits of atoms
b) Free electrons existing in nuclei
c) The decay of a neutron in nuclei
d) Photon escaping from the nucleus
Answer: c
Explanation: In β-emission, a neutron of nucleus decays into a proton and a β-particle.
The reaction given as:
0n1 ➔ 1H2 + -1e0.
4. Find the probability that the nucleus of 87Ra221 undergoes decay after three half-lives, if its a radioactive substance which has a half-life of 6 days.
a) 16
b) 32
c) 56
d) 12
Answer: c
Explanation: After one-half life, N02 sample remains and N02 decays.
After three half-lives, N06 sample remains and 5N06 decays.
Hence the probability that a nucleus undergoes decay after two half-lives is 56.
5. A 300-day old radioactive substance shows an activity of 5000 dps, 150 days later its activity becomes 2500 dps. What was its initial activity?
a) 25000 dps
b) 20000 dps
c) 32000 dps
d) 5000 dps
Answer: b
Explanation: The expression is given as:
R0 = 4R
4R = 4 × 5000
R0 = 20000dps.
6. Emission of β-rays in radioactive decay results in the change of either mass or charge.
a) True
b) False
Answer: b
Explanation: No, this is a false statement. The emission of β-rays can result in changes in the charge of the nucleus but not the mass of the nucleus. Mass of the nucleus is always conserved in radioactive decay.
7. Which will be the unknown nucleus formed when 22Ne10 decays into two α-particles and an unknown nucleus?
a) Fluorine
b) Carbon
c) Neon
d) Oxygen
Answer: b
Explanation: The reaction is given as:
22Ne10 ➔ 2 2He4 + 6X14.
Therefore, the unknown nucleus is 6C14.
8. What is the half-time of a radioactive sample (in minutes), if its mean life is 200 s?
a) 0.69 min
b) 2 min
c) 2.57 min
d) 2.31 min
Answer: d
Explanation: T1/2 = 0.693t
T1/2 = 0.693 × 200s
T1/2 = 138.660 min
T1/2 = 2.31 minutes
9. What will happen in a time of 7 hours, if a radioactive substance has an average life of 7 hours?
a) Half of the active nuclei decay
b) Less half of the active nuclei decay
c) More than half of the active nuclei decay
d) All active nuclei decay
Answer: c
Explanation: In one average life, i.e. at 7 hours, 63.2 % of the active nuclei will decay. Therefore, in a time of 7 hours, it can be considered that more than half of the active nuclei will decay.
10. A freshly prepared radioactive source of half-time 2h emits radiation of intensity which is 64 times the permissible safe level. Minimum time after which it would be possible to work safely with this source is which of the following?
a) 6 h
b) 12 h
c) 24 h
d) 20 h
Answer: b
Explanation: NN0=164.
t = n T1/2
t = 6 × 2hours
t = 12hours.
Nuclear Energy
1. Which of the following is an essential requirement for initiating the fusion reaction?
a) Critical mass
b) Thermal neutrons
c) High temperature
d) Critical temperature
Answer: c
Explanation: Two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles. High temperature is essential for initiating the fusion reaction. The others are not an essential requirement.
2. What is the reaction responsible for the production of light energy from the sun?
a) Fusion
b) Fission
c) Nuclear
d) Emission
Answer: a
Explanation: At very high temperatures in the interior of the sun, protons fuse to form helium nuclei, liberating a huge amount of energy. Therefore, the reaction responsible for the production of light energy from the sun is fusion.
3. What amount of energy is released by deuterium and tritium fusion?
a) 60.6 eV
b) 12.6 eV
c) 17.6 eV
d) 28.33 eV
Answer: c
Explanation: 1H2 + 1H3 ➔ 2He4 + 0n1 + Q.
= [2.014 + 3.016 – 4.002 – 1.008] × 931.5 MeV.
= 17.6 MeV.
4. In a nuclear reaction, there is the conservation of which of the following?
a) Mass only
b) Energy only
c) Momentum only
d) Mass, energy, and momentum
Answer: d
Explanation: Two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles. In any nuclear reaction, mass, energy, and momentum are conserved. So, all three are conserved.
5. Nuclear fission is possible in which of the following cases?
a) Only between light nuclei
b) Only between heavy nuclei
c) Between both light and heavy nuclei
d) Only between nuclei, which are stable against decay
Answer: a
Explanation: Nuclear fusion is possible between light nuclei. High temperature is essential for initiating the fusion reaction. Therefore, nuclear fission is possible only between light nuclei and not between heavy nuclei.
6. Solar energy is mainly caused due to fission of uranium present in the sun.
a) True
b) False
Answer: b
Explanation: No, this is a false statement. Solar energy is mainly caused due to the fusion of protons during the synthesis of heavier elements. So, it is not fission, but it is the fusion that results in solar energy.
7. Which of the following is used as a moderator in a nuclear reactor?
a) Cadmium
b) Plutonium
c) Uranium
d) Heavy water
Answer: d
Explanation: Heavy water is used as a moderator in a nuclear reactor. It slows down neutrons and also has a low probability of absorption of neutrons. The other options are not valid.
8. In nuclear reactors, what are the controlling rods made of?
a) Cadmium
b) Graphite
c) Stainless steel
d) Plutonium
Answer: a
Explanation: In nuclear reactors, cadmium rods are used as control rods. They are used to absorb the extra nucleons and to absorb neutrons, making them unavailable to cause fission. The other options are not valid.
9. The operation of a nuclear reactor is said to be critical if the multiplication factor (k) has a value of what?
a) 1
b) 0
c) 1.5
d) 2.1
Answer: a
Explanation: For a nuclear reactor, k = 1. It is the ratio of the number of neutrons produced in a nuclear pile to the number disappearing that must equal to unity for a chain reaction.
10. A neutron can cause fission in which of the following?
a) Hydrogen
b) Uranium-235
c) Thorium
d) Uranium-238
Answer: b
Explanation: A neutron, irrespective of whether it is slow or fast, can cause fission in a Uranium 235 nuclei. It absorbs a neutron and fissions into two new atoms by releasing some binding energy.