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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

β-rays

β-rays consist of fast moving electrons.

When a β-particle is emitted by a nucleus its atomic number is increases by 1 and mass number remains unchanged.

The emission of electron in β decay is accompanied by the emission of an antineutrino (ν); in β+ (positron) decay a neutrino (ν) is generated. Neutrinos are neutral particles with very small (possiblly, even zero) mass compared to electrons. They have only weak interaction with other particles. They are, therefore, very difficult to detect, since they can penetrate large quantity of matter (even earth) without any interaction.

n  p+e-+ν;      β-decay 

p  n+e++ν;       β+ decay

P1532  S1632 +e-+ν ;               β-decay 

Na1122  Ne1022 +e++ν;           β+ decay 

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