RBSE Class 12 Physics Chapter 13 — Nuclei: Most Repeated Questions (2013–2026)

(A) Nuclear fission is the process where a heavy nucleus (like Uranium-235) splits into two or more smaller, lighter nuclei, accompanied by the release of a large amount of energy and neutrons

(B) Nuclear fusion is the process where two or more light atomic nuclei (like isotopes of hydrogen) combine to form a single, heavier nucleus, releasing a massive amount of energy

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Mass Defect (∆m): It is the difference between the total mass of the constituent nucleons (protons and neutrons) in a nucleus and the actual measured mass of the nucleus

The actual nuclear mass is always less than the sum of its parts, i.e., Mass of nucleons > Actual nuclear mass

Nuclear Binding Energy (E_b): It is the minimum energy required to separate all the nucleons of a nucleus completely and infinitely apart

All solved questions for this chapter are in the full RBSE Physics PYQ book.

The nuclear force is the strongest attractive, short-range, charge-independent force that binds protons and neutrons (nucleons) together inside the tiny atomic nucleus, overcoming the electrostatic repulsion between the protons

The graph shows the binding energy per nucleon (in MeV) as a function of the mass number (A). It initially rises sharply from very light nuclei, peaking near A=56 (Iron, 56Fe), which has the highest binding energy per nucleon (around 8.8 MeV). This peak signifies the most stable nuclei. For A > 56, the binding energy per nucleon gradually decreases, indicating that very heavy nuclei like 238U are less stable than medium-sized nuclei. The stability of nuclei is directly related to the binding energy per nucleon

All solved questions for this chapter are in the full RBSE Physics PYQ book.

Mass Defect (∆m): It is the difference between the total mass of the constituent nucleons (protons and neutrons) in a nucleus and the actual measured mass of the nucleus

The actual nuclear mass is always less than the sum of its parts, i.e., Mass of nucleons > Actual nuclear mass

Binding Energy per Nucleon = Total binding energy/mass number

Mass number =16

Binding Energy per Nucleon = 127.5MeV/16

=7.97MeV

1eV=1.602×10^-19J

All solved questions for this chapter are in the full RBSE Physics PYQ book.

ρ=M/V

M≈A⋅m

V=4/3πR³

R=R₀A^1/3

V=4/3π(R₀A^1/3)³

V=4/3πR₀³(A^1/3)³

V=4/3πR₀³A

ρ=M/V=A⋅m/(4/3πR₀³A)

ρ=3m/4πR₀³

Since m (average nucleon mass), π , and R₀ (the radius constant) are all constants, the entire expression for ρ is a constant

All solved questions for this chapter are in the full RBSE Physics PYQ book.