AIIMS Physics Nuclei Class 12 Questions

Find BE per nucleon of ⁵⁶Fe where m(⁵⁶Fe) = 55.936 u, mₙ = 1.00727 u, mₚ = 1.007274 u.

P.E.T. is positron emission tomography is a nuclear medicine functional imaging technique used to observe metabolic processes to diagnosis of disease.

The number of nuclei decayed in 1 year is calculated as, \(-rac{dN}{dt} = \lambda N\) \(-dN = rac{\ln 2}{T} imes N imes dt\) \(= rac{0.7}{10^{33}} imes 26 imes 10^{24} imes 1\) \(= 18.2 imes 10^{-7}\)

If half life of an element is 69.3 hours then how much of its percent will decay in 10th to 11th hours. Initial activity = 50 µCi

The binding energy increases with increase in the atomic mass number due to the attractive nuclear forces between the nucleons. Larger the number of nucleons, more tightly they are bound together. The density of nucleus is given by, ρ = \( \frac{3m}{4\pi r_0^3} \) Here, m is the mass of a nucleon and r₀ is the Bohr radius. The above equation shows that density is independent on the mass number. Hence, assertion is true but reason is false.

The decay rate is given as, N = N₀(1/2)ⁿ. The number of half lives is calculated as, 2ⁿ = 100. n lies between the 6 and 7. So, the radioactive element will decay between 6 and 7 half lives.

The principle of controlled chain reaction is used in

In U₂₃₅ fission reaction neutrons are required to be slowed down because the probability of capture of slow moving neutrons is high for U₂₃₅.

Assertion: Heavy water is used to slow down neutron in nuclear reactor Reason: It does not react with slow speed neutron and mass of deuterium is comparable to the neutron

Assertion: Radioactive nuclei emit β⁻¹ particles.

If decay constant of a radioactive sample is 0.05/year, then find out the time for which sample will decay by 75%.

A nuclear explosive is designed to deliver 1 MW power in the form of heat energy. If the explosion is designed with nuclear fuel consisting of U²³⁵ to run a reactor at this power level for one year, then the amount of fuel needed is (Given energy per fission is 200 MeV)

In the following questions, a statement of assertion is given followed by a corresponding statement of reason. Assertion: In a decay atom number of daughter nucleus reduces by 2 from the parent nucleus. Reason: An Q⁻particle carries four units of mass.

Assertion (A) Forces acting between proton-proton (fₚₚ), proton-neutron(fₚₙ) and neutron-neutron (fₙₙ) are such that fₚₚ < fₚₙ = fₙₙ Reason (R) Electrostatic force of repulsion between two protons reduces net nuclear forces between them.

At a specific instant emission of radioactive compound is deflected in a magnetic field. The compound can emit

In nuclear fission, which of the following quantity is conserved?

When a slow neutron is captured by a ²³⁵U nucleus, a fission energy releasing 200 MeV. If power of nuclear reactor is 100 W then rate of nuclear fission is

Which of the following statement is incorrect?

In beta plus decay

Half life of a radio-active element is 8 years, how much amount will be present after 32 years?

Gamma decay takes place

The nucleus \( _{Z}^{A}X \) emits one α particle and 2β-particles. The resulting nucleus is

Assertion: At rest, radium is decayed into Radon and an α-particle. They both moves back to back of each other. Reason: Splitting of radioactive particle is based on conservation of linear momentum.

Assertion: More energy is released in fusion than fission. Reason: More number of nucleons take part in fission.

Assertion: $\gamma$-radiation emission occurs after $\alpha$ and $\beta$ decay. Reason: Energy levels occur in nucleus.

The ratio of the masses of the elements having their nuclear radii 2 fermi and 1 fermi is

For a nuclear reactor to run in critical condition the reproduction factor k should be

S₃₂ absorbs energy and decays into which element after two α-emissions?

Half life of a radioactive material is 5 years, then the percentage of it remained after 25 years will be

Among the following which is used to control the rate of reaction in nuclear fission reactions?

Assertion: For nuclear reactor, it is desirable to have k = 1. Reason: Sustained chain reaction occur at this critical condition.

Assertion : Mass defect in nuclear reactions is less than 1% Reason : In nuclear reaction, change in B/E/N is generally less than 1%.

Assertion : It is desirable to slow down fast moving neutrons to sustain controlled chain reactions. Reason : Slow moving neutrons efficiently collides with U²³⁵.

A nucleus of mass number 220 decays by \( \alpha \) decay. The energy released in the reaction is 5 MeV. The kinetic energy of an \( \alpha \)⁻particle is

The wavelengths of K\( \alpha \) X⁻rays for lead isotopes \( ^{208}Pb, ^{206}Pb \) and \( ^{204}Pb \) are \( \lambda_2, \lambda_4 \) and \( \lambda_3 \) respectively.

Assertion : Nuclei having number about 60 are most stable. Reason : When two or more light nuclei are combined into a heavier nucleus, then the binding energy per nucleon will increase.

What is the amount of energy released by deuterium and tritium fusion?

Calculate power output of ²³⁵U reactor, if it takes 30 days to use up 2 kg of fuel, and if each fission gives 185 MeV of useable energy. Avogadro's number = 6 × 10²³/mol?

Assertion : Heavy water is a better moderator than normal water. Reason : Heavy water absorbs neutrons more efficiently than normal water.

Assertion : ⁹⁰Sr from the radioactive fall out from a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells. Reason : The energetics β-particles emitted in the decay of ⁹⁰Sr damage the bone marrow.

The operation of a nuclear reactor is said to be critical, if the multiplication factor (k) has a value

²³⁸U₉₂ has 92 protons and 238 nucleons. It decays by emitting an alpha particle and becomes

Which one of the following is a possible nuclear reaction?

Assertion : The binding energy per nucleon, for nuclei with atomic mass number A > 100 decreases with A. Reason : The nuclear forces are weak for heavier nuclei.

Assertion : It is not possible to use ³⁵Cl as the fuel for fusion energy. Reason : The binding energy of ³⁵Cl is too small.

A nucleus of mass number A, originally at rest, emits an α-particle with speed v. The daughter nucleus recoils with a speed

When an electron-positron pair annihilates, the energy released is about

The dependence of binding energy per nucleon, Bₑ, on the mass number A, is represented by

Assertion : Energy is released in nuclear fission. Reason : Total binding energy of the fission fragments is larger than the total binding energy of the parent nucleus.

Assertion : Heavy water preferred over ordinary water as a moderator in reactors. Reason : Heavy water, used for slowing down the neutrons, has lesser absorption probability of neutrons than ordinary water.