Nuclei

Nuclear force has the following properties (i) Nuclear force is a short range force whose range is of the order of 2 to 3 femtometre (ii) Nuclear force is the strongest force in nature (iii) Nuclear force is an attractive force acting between nucleons, which is charge independent. Therefore, nuclear force is strong, short range and charge independent force.

Energy released from 1 kg of uranium

Nuclides with same atomic number but different mass number A are known as isotopes Nuclides with same mass number but different atomic number are known as isobars Nuclides with same neutron number but different atomic number are known as isotones and are isotopes and are isobars and are isotones

Answer (d) hydrogen is burned into helium

Concept:

Step 1: Ratio.

Step 1: Understanding the Concept:
Different nuclear processes involve the emission of different particles.

Step 2: Detailed Explanation:

• -decay: Emits an alpha particle ( nucleus).
• -decay: Emits an electron ( ) or positron.
• Nuclear fusion: Two light nuclei combine to form a heavier nucleus, releasing energy, but not typically free neutrons as a primary product (though some fusion reactions like D+T produce neutrons).
• Pair production: A photon creates an electron-positron pair. No neutrons.
• Nuclear fission: A heavy nucleus (e.g., U-235) splits into two lighter nuclei, and typically 2-3 free neutrons are released. This is the process that releases neutrons from the nucleus.

Step 3: Final Answer:
Nuclear fission releases neutrons.

Concept:
Physics - Nuclear Physics (Binding Energy Curve).
Step 1: Define Binding Energy per Nucleon.
Binding energy per nucleon is the total binding energy of a nucleus divided by its mass number ( ). It is a direct measure of nuclear stability.
Step 2: Analyze the Binding Energy Curve.
When we plot binding energy per nucleon against mass number:

• It is low for very light nuclei (fusion region).
• It is low for very heavy nuclei (fission region).
• It peaks in the middle of the periodic table.

[Image of binding energy per nucleon curve]
Step 3: Identify the peak point.
The curve reaches its maximum value of approximately MeV per nucleon for Iron-56 ( ).
Step 4: Conclusion.
Iron ( ) is the most stable nucleus because it has the highest binding energy per nucleon.

Step 1: Understanding the Concept:
This is a theoretical knowledge question based on the principles of nuclear physics, specifically regarding the induced nuclear fission of Uranium-235 ( ).

Step 2: Detailed Explanation:
When a slow (thermal) neutron strikes a nucleus, it makes the nucleus highly unstable ( ), causing it to undergo fission.
The nucleus splits into two lighter, intermediate-mass fission fragments.
To conserve nucleons, this process also emits several secondary neutrons.
Depending on the specific fission fragment pair created, 2, 3, or sometimes more neutrons are ejected. Experimental data shows that the average number of neutrons released per fission is approximately 2.47, which is conventionally rounded to in general physics problems.
These newly born secondary neutrons are emitted with high kinetic energy. They are termed "fast neutrons".
The average kinetic energy of these fast neutrons emitted during fission is known to be approximately (Mega-electron Volts).
Therefore, on average, neutrons are released, each possessing an energy of roughly .

Step 3: Final Answer:
The correct pair of values is and , corresponding to option (C).

Concept:
• Number of atoms:
• Total energy:

Step 1: Number of atoms


Step 2: Total energy
Final Conclusion:
Option (A)