AIIMS Physics Nuclei Class 12 Questions

A sample which has half life of $10^{33}$ years, if the initial number of nuclei of the sample is $26 \times 10^{24}$. Then find out the number of nuclei decayed in 1 year.

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

99% of a radioactive element will decay between

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

The luminous dials watches are usually made by mixing a zinc sulphide phosphor with an α particle emitter. The mass of radium (mass number 226, half-life 1620 years) that is needed to produce an average of 10 α-particles per second for this purpose is

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.

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

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.

Nuclear fusion is possible

Assertion : Radioactive nuclei emit β⁻ particles. Reason : Electrons exist inside the nucleus.

Assertion : Neutrons penetrate matter more readily as compared to protons. Reason : Neutrons are slightly more massive than protons.

If mass of an atom is M moving with speed v, what will be its speed after the emission of an α-particle if speed of α-particle is zero ?

Assertion: Density of all the nuclei is same. Reason: Radius of nucleus is directly proportional to the cube root of mass number.