Nuclei: Class 12 Physics Chapter 13 Notes in Hindi

the genius April 08, 2026

 

Nuclei: Class 12 Physics Chapter 13 Notes in Hindi

Pichle chapter mein humne Atom ke baare mein padha. Is chapter mein hum Nucleus ke andar maujood Protons aur Neutrons (jinhe milakar Nucleons kehte hain) ke baare mein jaanenge. Yeh chapter Nuclear Energy aur Radioactivity ke concepts ke liye bahut zaroori hai.

1. Composition of Nucleus

Nucleus do tarah ke particles se bana hota hai:

  • Atomic Number (Z): Nucleus mein maujood Protons ki sankhya.

  • Mass Number (A): Protons aur Neutrons ka total sum ($A = Z + N$).

  • Isotopes: Jinka $Z$ same ho par $A$ alag ho (e.g., $^1H_1, ^2H_1, ^3H_1$).

  • Isobars: Jinka $A$ same ho par $Z$ alag ho.

  • Isotones: Jinmein Neutrons ki sankhya ($N$) barabar ho.

2. Size and Density of Nucleus

Nucleus ka volume uske mass number ke proportional hota hai.

  • Radius Formula:

    $$R = R_0 A^{1/3}$$

    (Yahan $R_0 \approx 1.2 \times 10^{-15}$ m ya 1.2 fermi hai).

  • Nuclear Density: Sabhi nuclei ki density lagbhag constant hoti hai ($2.3 \times 10^{17} kg/m^3$), jo ki pani ki density se 14 trillion guna zyada hai!

3. Mass Defect and Binding Energy

Yeh is chapter ka sabse important concept hai.

  • Mass Defect ($\Delta m$): Nucleus ka asli mass, uske alag-alag nucleons ke total mass se hamesha thoda kam hota hai. Is antar ko Mass Defect kehte hain.

  • Binding Energy ($E_b$): Einstein ke mutabik ($E = \Delta mc^2$), jo mass gayab hota hai wahi energy ban kar nucleons ko nucleus mein bandhe rakhta hai.

  • Binding Energy per Nucleon: Yeh batati hai ki nucleus kitna stable hai. Iron ($Fe$) sabse zyada stable nucleus hai.

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4. Nuclear Forces

Nucleus ke andar protons ek dusre ko repel karte hain, fir bhi saath rehte hain. Iska kaaran hai Strong Nuclear Force.

  • Yeh nature ka sabse takatwar force hai.

  • Yeh sirf bahut choti doori (short-range) par kaam karta hai.

  • Yeh charge par depend nahi karta (Proton-Proton aur Neutron-Neutron ke beech barabar lagta hai).

5. Nuclear Fission and Fusion

Nuclear energy do tareekon se milti hai:

  1. Nuclear Fission (Vikhondan): Jab ek bhari nucleus (jaise Uranium) do halke nuclei mein toot-ta hai. Yeh Atomic Bomb aur Nuclear Reactor ka base hai.

  2. Nuclear Fusion (Sallayan): Jab do halke nuclei milkar ek bhari nucleus banate hain. Isme fission se bhi zyada energy nikalti hai. Yeh Suraj (Sun) aur Hydrogen Bomb ki energy ka source hai.

6. Top Important Questions (Chapter 13)

Short Questions (1-2 Marks):

  1. 1 amu (Atomic Mass Unit) kitni energy ke barabar hai? $931.5 MeV$.

  2. Nuclear density mass number par kaise depend karti hai? Yeh depend nahi karti, sabhi ke liye constant hoti hai.

  3. Nuclear Fusion ke liye high temperature kyun chahiye? Taaki nuclei repulsion ko par karke ek dusre ke paas aa sakein.

Long & Numerical Questions (3-5 Marks):

  1. Draw the Binding Energy Curve and explain its main features.

  2. Differentiate between Nuclear Fission and Fusion.

  3. Explain the properties of Nuclear Forces.

  4. Calculate the mass defect and binding energy of a given nucleus. (Numerical practice zaroori hai).

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