Nuclear Fission MCQ Quiz - Objective Question with Answer for Nuclear Fission - Download Free PDF

Given:

Consider the nuclear fission reaction:

¹n + ²³⁵U₉₂ → ¹⁴⁴Ba₅₆ + ⁸⁹Kr₃₆ + 3¹n

Total binding energies:

• Binding energy of ²³⁵U₉₂ = 1800 MeV
• Binding energy of ¹⁴⁴Ba₅₆ = 1200 MeV
• Binding energy of ⁸⁹Kr₃₆ = 780 MeV

Concept:

Energy released = (Binding energy of products) - (Binding energy of reactants)

Average kinetic energy = (Energy released) / Number of neutrons

• During nuclear fission, the total energy released is carried away as kinetic energy by the fission fragments and fast neutrons.
• Energy released in the fission reaction is given by:
• Assuming all the energy is carried away by fast neutrons, the average kinetic energy per neutron is:

Calculation:

Step-by-step calculation:

⇒ Total binding energy of products:

= Binding energy of ¹⁴⁴Ba₅₆ + Binding energy of ⁸⁹Kr₃₆

= 1200 + 780 = 1980 MeV

⇒ Energy released:

= Binding energy of products - Binding energy of reactants

= 1980 - 1800 = 180 MeV

⇒ Number of fast neutrons = 3

⇒ Average kinetic energy per neutron:

= Energy released / Number of neutrons

= 180 / 3 = 60 MeV

∴ The average kinetic energy carried by each fast neutron is 60 MeV.

The correct option is 4).

Concept:

In the proton-proton cycle in the Sun, when an electron and its antiparticle combine, energy is released. This is a form of matter-antimatter annihilation.

The energy released during this annihilation can be calculated using Einstein’s mass-energy equivalence formula:

E = mc²

Where:

• E is the energy released
• m is the mass of the electron and positron (which is the same as that of the electron, 9.11 × 10^-31 kg)
• c is the speed of light (3 × 10⁸ m/s)

Calculation:

Thus, the energy released when the electron and its antiparticle combine is given by:

E = 2 × (9.11 × 10^-31) × (3 × 10⁸)² = 1.021 × 10^-13 J

The correct answer is 1.021 × 10^-13 J, as given in option 1.

Calculation:
Total mass number of ₉₄²³⁹ Pu + neutron (thermal) = 239 + 1 = 240. Since 4 neutrons are produced, the mass number of each fragment is:

A = (240 - 4) / 2 = 118

The atomic number of each fragment is:

94 / 2 = 47

Therefore, the charge of each fragment is:

q = 47 × 1.6 × 10^-19 = 7.52 × 10^-18 C

The radius of each nucleus of the fragment is:

R = R₀ × (A)^1/3 = 1.1 × 10^-15 × (118)^1/3 = 5.395 × 10^-15 m

The distance between the centres of the two fragments at the moment they are produced is:

r = 2 × 5.395 × 10^-15 = 10.79 × 10^-15 m

The electrostatic force between them is:

F = (1 / 4πε₀) × (q² / r²) = 9 × 10⁹ × ((7.52 × 10^-18)² / (10.79 × 10^-15)²) = 4.37 × 10³ N

\(\rm Q=\left(m_{N}+m_{H e}-m_{H}-m_{O}\right) \times c^{2}\)

= (16.006 + 4.003 - 1.008 - 19.003) × 930 MeV

= - 1.86 MeV

= 1.86 MeV energy absorbed

And, \(\frac{1}{2} \times \frac{m \times 4 m}{5 m} \times v^{2}\) = max loss in kinetic energy

\(\Rightarrow \frac{1}{2} m v^{2}=\frac{5}{4} \times Q\)

\(=\frac{5}{4} \times(1.86) \mathrm{MeV}\)

= 2.325 MeV

∴ n = 2.33

Concept:

The nuclear reaction is: ²³⁶₉₂U → ¹⁴⁰₅₄Xe + ⁹⁴₃₈Sr + x + y

From conservation of charge, the total charge on the left-hand side is 92. On the right-hand side, the combined charge of Xe and Sr is 54 + 38 = 92. Therefore, x and y must be neutral overall. So, any option with net charge (like proton + neutron) is invalid.

Explanation:

Option C (proton + neutron) is ruled out since their combined charge is not zero.

Change in binding energy (ΔBE):

ΔBE = –236 × 7.5 + 140 × 8.5 + 94 × 8.5 = 219 MeV

This energy is released as the total kinetic energy of the fission products.

Conservation of momentum:

Initial momentum is zero (since the nucleus was at rest), so the momenta of products must cancel out. That means lighter products must have higher velocity and kinetic energy.

Case Analysis:

• Case A: If x and y are both neutrons, they are neutral, and conservation laws are satisfied. Also, Sr being lighter will have more kinetic energy. This is consistent.
• Case D: Sr has less kinetic energy, which contradicts the above logic. So, this is not possible.
• Case B: Electron is a lepton. Lepton number conservation would not be satisfied if leptons appear without corresponding antileptons or justification.

The correct option is (A).

Concept:

• The nucleus of a heavy atom (such as uranium, plutonium or thorium), when bombarded with low-energy neutrons, can be split apart into lighter nuclei. This process is called nuclear fission.
• Fission occurs when a neutron slams into a larger atom, forcing it to excite and split into two smaller atoms—also known as fission products.
• A chain reaction refers to a process in which neutrons released in fission reaction produces an additional fission reaction in at least one further nucleus. This nucleus, in turn, produces neutrons, and the process repeats.

• During this reaction, a tremendous amount of energy is released.

Explanation:

• Fission reaction can further be classified into controlled and uncontrolled fission reaction.
• In controlled fission the chain reaction is controlled and only a controlled amount of reaction is allowed, nuclear reactors in nuclear power plants are one of the examples of the controlled fission reaction.
• And for uncontrolled fission chain reaction it is allowed to happen unless fission material is over, atomic bomb is one of the examples of an uncontrolled fission reaction.

The correct answer is Nuclear Fusion.

Key Points

• Sun Energy
  • All things on earth are in constant need of energy in some or another way.
  • Human beings and animals obtain energy from their food.
  • That is indirectly obtained from plants.
  • Plants acquire energy through photosynthesis where they convert light energy from the sun into their useful form of energy.
  • Moon also gets its light from the reflection of sunlight.
  • Hence the only source that constantly gives us energy is the sun.
  • In the sun, energy is produced by nuclear fusion. Hence, Option 1 is correct.
  • Nuclear fusion occurs when two hydrogen atoms fuse to form helium atoms.
  • When the hydrogen atoms in the sun get over, the helium atoms will start fusing to form carbon atoms, then carbon atoms fuse to form silicon and the reaction will end when the final atoms left in the sun become Iron.
  • Since iron is the most stable element, iron will not undergo further fusion.
  • Thus the energy production in the sun will end, resulting in the collapse of the sun and eventually leads to the death of the sun.

Additional Information

• Nuclear fission
  • It is the process of splitting apart nuclei (usually large nuclei).
  • When large nuclei, such as uranium-235, fissions, energy is released.
  • So much energy is released that there is a measurable decrease in mass, from the mass-energy equivalence.
  • This means that some of the mass is converted to energy.
• A chemical reaction
  • It is a process that leads to the chemical transformation of one set of chemical substances to another.
• Mechanical energy
  • It is the sum of potential energy and kinetic energy.
  • It is the macroscopic energy associated with a system.
  • The principle of conservation of mechanical energy states that if an isolated system is subject only to conservative forces, then the mechanical energy is constant.

Annihilation is the complete destruction of an object. In Physics, when a particle and its antiparticle collide and disappears and release energy, It's called Annihilation.

Electron-Positron Annihilation:

1) The most common annihilation on earth is between an electron and its antiparticle, a positron.

2) They annihilate and disappear, giving off two gamma-rays in the process.

3) The particles appear to have vanished and all energy is transferred to gamma rays (photons).

The amount of energy (E) produced by annihilation is equal to the mass (m) that disappears multiplied by the square of the speed of light in a vacuum (c).

E = mc² 

The rest mass of an electron and positron is 9.109×10⁻³¹ kg

The energy released when both collide:

E = 2 ×  mc2 

E = 2 × 9.109×10−31 × (3 × 10⁸)²

E = 163.962 × 10^-15 J

Now, we know that 1 eV = 1.602 × 10^-19 J

∴ The energy released in Electron-volt (eV) will be:

= \(\frac{163.962 ×10^{-15}}{1.6×10^{-19}} ~eV\) 

= 102.47 × 10⁴ eV

= 1.02 MeV

The correct answer is Nuclear Fusion.

Key Points

• Nuclear fusion is the process where the nuclei of two light atoms combine to form a  new nucleus.
• Nuclear Fusion is a reaction in which two or more atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles (neutrons or protons). The difference in mass between reactant and products is manifested as either the release of the absorption of energy. This difference in mass arises due to the difference in atomic binding energy between the nuclei before and after the reaction.
• Fusion is the process that powers active or main sequence stars and other high-magnitude stars, where large amounts of energy are released.
• The fusion process that produces nuclei lighter than iron-56 or nickel=62 will generally release energy. These elements have a relatively small mass per nucleon and large binding energy per nucleon.
• A fusion of nuclei lighter than these releases energy (exothermic process) while the fusion of heavier nuclei results in energy retained by the product nucleons and the resulting reaction is endothermic.

Image of the working process of the Nuclear Fusion:

Additional Information

• The nucleus of a heavy atom (such as uranium, plutonium, or thorium), when bombarded with low-energy neutrons, can be split apart into lighter nuclei. This process is called nuclear fission.
• Fission occurs when a neutron slams into a larger atom, forcing it to excite and split into two smaller atoms—also known as fission products.
• A chain reaction refers to a process in which neutrons released in fission reaction produces an additional fission reaction in at least one further nucleus. This nucleus, in turn, produces neutrons, and the process repeats.

• During this reaction, a tremendous amount of energy is released.

Important Points

• Fission reaction can further be classified into controlled and uncontrolled fission reaction.
• In controlled fission, the chain reaction is controlled and only a controlled amount of reaction is allowed, nuclear reactors in nuclear power plants are one of the examples of the controlled fission reaction.
• And for an uncontrolled fission chain reaction, and it is allowed to happen unless fission material is over, the atomic bomb is one of the examples of an uncontrolled fission reaction.

Concept:

Nuclear fission:

• A nuclear fission reaction occurs inside a nuclear reactor.
• In a fission reaction, an element is bombarded with low energy neutron.

• This leads to the production of new elements and more neutrons.
• The neutrons produced bombards with other elements and a series of chain reactions gets started.

• A great amount of energy is produced in this process which is utilized for variable purposes.

Explanation:

• In nuclear reactors, fuels are used for nuclear reactions.
• The fuel undergoes fission to produce energy.
• Mostly, heavy fissile elements such as actinoids are used in this type of reactors.
• U-235 and Pu-239 are mostly used in nuclear reactors as fuels.
• Uranium-235 is a naturally occurring fissile isotope, and it is widely used in nuclear power plants and nuclear weapons.
• Whereas, Pu - 239 is artificial and synthesized from the transmutation of U- 238.
• When U - 238 is exposed to neutron radiation in nuclear reactors, it decays to Pu - 239.
• Th232 is not used as a fuel in nuclear reactors.

Thus, Pu-239 is an artificial fuel.

Explanation:

Fossil Fuels:

• Fossil fuels are formed by natural processes such as anaerobic decomposition of buried organisms under heat and pressure.
• Fossil fuels like coal, petroleum, natural gas contain high percentages of carbon.
• Fossil fuels are non-renewable resources and must be burned to release their energy.
• It releases sulphur, nitrogen, carbon, etc. gases in the atmosphere which causes the greenhouse effect and pollution.

The correct answer is Uranium.

• Some exhaustible natural resources like coal, petroleum and natural gas,
  • These were formed from the dead remains of living organisms (fossils).
  • So, these are all known as fossil fuels.
• Coal is one of the fuels used to cook food.
  • Earlier, it was used in railway engines to produce steam to run the engine.
  • It is also used in thermal power plants to produce electricity. Coal is also used as fuel in various industries.
• Petroleum was formed from organisms living in the sea.
  • As these organisms died, their bodies settled at the bottom of the sea and got covered with layers of sand and clay.
• Over millions of years, absence of air, high temperature and high pressure transformed the dead organisms into petroleum and natural gas.
• A natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.

Unlike coal or crude oil, Uranium does not remain of a prehistoric organism, and therefore it is not fossil fuel - it's just fuel.

Additional Information

Uranium is the fuel most widely used by nuclear plants.

With the help of fission process-

Nuclear fission is a nuclear reaction process in which a heavy nucleus splits into two nuclei of nearly equal mass.

• Example – Uranium (235) breaks into Barium (141) and Krypton (92) with a lot of energy.

The correct answer is option 1: A hydrogen bomb creates a devastating explosion because of nuclear fission and nuclear fusion,

• A Hydrogen Bomb is also known as a thermonuclear bomb or a fusion bomb.
• The hydrogen bomb is considered to be highly dangerous as compared to the Atomic bomb.

Hydrogen Bomb:

• The hydrogen bomb uses Uranium or Plutonium for fission reactions and isotopes of hydrogen for the fusion reaction
• Principle:
  • The basic Principle of a Hydrogen bomb is nuclear fusion.
  • Deuterium and Tritium, the isotopes of hydrogen are used in fusion bombs.
  • The nuclei of these atoms fuse together to form bigger nuclei generally that of Helium.
• Working:
  • To start the fusion reaction a high amount of energy is required initially.
  • This energy is supplied by nuclear fission reactions.
  • Therefore, a high amount of energy is first released by the nuclear fission reaction.
  • Then a portion of the energy is used for Nuclear fusion reactions which creates a more devastating explosion.

Nuclear Fission:

• In this reaction, a bigger nucleus splits into smaller nuclei and neutrons with the release of energy.
• The most common example of this is the fission of Uranium into Barium and Krypton.
• Atomic bombs (Little Boy and Fat Man) dropped on Hiroshima and Nagasaki used fission reactions.
• Nuclear power plants also work on the principle of fission but in a controlled manner.

Nuclear Fusion:

• The fusion of smaller nuclei to form a bigger one refers to Nuclear Fusion.
• The fusion of hydrogen isotopes to form a helium nucleus is an example.
• Fusion bombs have never been used in warfare till date.
• Fusion reaction is the source of energy in the sun.

Mistake Points

• Both Nuclear fusion and fission are used in Hydrogen bombs.
• It is the atomic bomb that uses only Fission.
• In fact, the main difference between atomic bombs and hydrogen bombs is that the Hydrogen uses a combination of nuclear fission and nuclear fusion both.

Concept:

• The nucleus of a heavy atom (such as uranium, plutonium or thorium), when bombarded with low-energy neutrons, can be split apart into lighter nuclei. This process is called nuclear fission.
• Fission occurs when a neutron slams into a larger atom, forcing it to excite and split into two smaller atoms—also known as fission products.
• A chain reaction refers to a process in which neutrons released in a fission reaction produces an additional fission reaction in at least one further nucleus. This nucleus, in turn, produces neutrons, and the process repeats.

• During this reaction, a tremendous amount of energy is released.
• The nuclear reactors are controlled by means of control rods which are made of a strongly neutron-absorbent material such as boron or cadmium (Cd).

Explanation:

During nuclear fission, a heavy nucleus breaks into two or more daughter nuclei with a lighter mass. The total binding energy of these daughter nuclei is greater than the parent nuclei. Greater binding energy means a larger amount of energy is released during the formation of a nucleus. This difference in binding energy accounts for the release of energy during nuclear fission.

The correct answer is option (1)

Key Points

Nuclear Fission:

The nuclear reaction in which a heavy nucleus splits into two nuclei of nearly equal mass is called nuclear fission.

• Chain Reaction:

• When a uranium atom is bombarded with slow neutrons, fission takes place. With the fission of each uranium nucleus, on average, three neutrons and large energy are released.
• These neutrons cause further fission. Clearly, a chain of fission of uranium nucleus starts which continues till the whole of uranium is exhausted. This is called a chain reaction.
• The atom bomb is based on nuclear fission.
  • U-235 and Pu-239 are used as fissionable materials.
• A nuclear reactor is an arrangement in which a controlled nuclear fission reaction takes place.

The correct answer is Nuclear reactors.

Additional Information

• Nuclear Fusion: When two or more light nuclei combined together to form a heavier nucleus, tremendous energy is released.
• The energy released by the sun and other stars is by nuclear fusion.
• Hydrogen bomb:
  • The hydrogen bomb was made by American scientists in 1952.
  • This is based on nuclear fusion.
  • It is 1000 times more powerful than the atom bomb.

The correct option is the minimum mass needed for chain reaction. 

Concept:

• Nuclear Fission: In nuclear fission, a heavy atom, such as uranium or plutonium, breaks into two or more smaller nuclei along with certain byproducts, such as neutrons and photons (energy). 
• Nuclear Fusion: In contrast to nuclear fission, nuclear fusion involves fusing light nuclei, such as deuterium and tritium from the hydrogen isotope family, to create heavier nuclei, such as helium, and a massive quantity of energy. 

Expanation:

• A sustained nuclear chain reaction requires a critical mass, which is the least amount of fissile material.
• The precise amount relies on the material's purity and geometry, density, form, and amount, as well as its density and nuclear properties (such as its nuclear fission cross-section).
• Critical mass is the minimum amount of fissile material needed to maintain a nuclear chain reaction.

Additional Information • A Hydrogen bomb is based on the principle of uncontrollable nuclear fusion.
• A continuous chain reaction is required in a nuclear reactor. So, this concept is used in a nuclear reactor.
• Mass defect is a fundamental property of a nucleus and is a fixed value corresponding to a certain amount of binding for that nucleus.