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CBSE NOTES CLASS 12 PHYSICS

CHAPTER 13 NUCLEUS

Subatomic particles

Nucleus

Nucleons

Atomic mass unit

Mass energy

Mass defect

Nuclear force

Nuclear binding energy

Binding energy per nucleon

Properties of binding force and binding energy

Relation of nuclear size and atomic mass number

Nuclear density

Isotopes

Isobars

Isotones

Isomers

Radioactivity

α-rays

β-rays

γ-rays

Law of radioactive decay

Rate of decay of nucleus

Half-life of a radioactive element

Average life or mean life of a radioactive element (τ)

Nuclear fission

Structure of nuclear reactor

Nuclear fuel

Moderator

Control rods

Coolant in nuclear reactor

Pressure vessel or pressure tubes in nuclear reactor

Steam generator in nuclear reactor

Nuclear fusion

The proton-proton (p, p) cycle in the sun

CBSE NOTES CLASS 12 PHYSICS

CHAPTER 13 NUCLEUS

α-rays

α-rays consists of α-particles, which are doubly ionised helium ion.

When an α-particle is emitted by a nucleus its atomic number decreases by 2 and mass number decreases by 4.

XZA  YZ-2A-4 +He24

Example

U92238  Th90234 +He24

Total mass of RHS is less than that of LHS.

The disintegration energy or the Q-value of a nuclear reaction is the difference between the initial mass energy and the total mass energy of the decay products. For α-decay

Q = [mX  (mY + mHe)] c2

Q is also the net kinetic energy gained in the process or, if the initial nucleus X is at rest, the kinetic energy of the products, Q > 0 for exothermic processes such as α-decay.

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