Given below are two statements: Statement I : For all elements, greater the mass of the nucleus, greater is the binding energy per nucleon. Statement II : For all elements, nuclei with less binding energy per nucleon transforms to nuclei with greater binding energy per nucleon. In the light of the above statements, choose the correct answer from the options given below:

Solution & Explanation

Core Logic

Statement I: The binding energy per nucleon does not monotonically increase with mass. It reaches a maximum around iron (A ≈ 56) and then gradually decreases for heavier nuclei. Hence, Statement I is false.

Statement II: Nuclei inherently tend toward states of greater stability. Thus, nuclei with lower binding energy per nucleon undergo reactions (fission or fusion) to form nuclei with higher binding energy per nucleon. Hence, Statement II is true.

Step 1: Final Conclusion

Statement I is false but Statement II is true. Therefore, option (4) is correct.

Pattern Recognition

The binding energy curve is a classic plateau curve peaking at Iron-56. Statements claiming monotonic trends across all masses in nuclear physics are generally false.

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Class 12 Physics: Nuclei

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Q45 jee_main_2024_31_jan_evening Nuclear Radius
The mass number of nucleus having radius equal to half of the radius of nucleus with mass number 192 is:
  • A. 24
  • B. 32
  • C. 40
  • D. 20

Solution

Related Formula

Nuclear radius is empirically related to mass number by: R = R₀ A1/3

Core Logic

Given R₁ = (R₂)/(2) where A₂ = 192. We need to find A₁.

Step 1: Forming the Ratio
(R₁)/(R₂) = ((A₁)/(A₂))1/3 (1)/(2) = ((A₁)/(192))1/3
Step 2: Cubing Both Sides
((1)/(2))³ = (A₁)/(192) (1)/(8) = (A₁)/(192) A₁ = (192)/(8) = 24
Pattern Recognition

Since R ∝ A1/3, scaling R by k means scaling A by k³. Half the radius (k = 1/2) means 1/8th the mass number.

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Class 12 Physics: Nuclei

Q60 jee_main_2024_31_jan_evening Nuclear Size and Density
A nucleus has mass number A₁ and volume V₁. Another nucleus has mass number A₂ and volume V₂. If relation between mass number is A₂ = 4A₁, then (V₂)/(V₁) = ________.
Numerical Answer. Answer: 4 to 4

Solution

Related Formula

R = R₀ A1/3

V = (4)/(3)π R³
Core Logic

Since radius R is proportional to A1/3, the volume V (which depends on R³) will be directly proportional to the mass number A.

Step 1: Show Proportionality
V = (4)/(3)π (R₀ A1/3)³ = (4)/(3)π R₀³ A

This proves that V ∝ A.

Step 2: Calculate Ratio
(V₂)/(V₁) = (A₂)/(A₁)

Given that A₂ = 4A₁:

(V₂)/(V₁) = (4A₁)/(A₁) = 4
Pattern Recognition

Nuclear density is constant for all nuclei. Therefore, Mass ∝ Volume. Since Mass number (A) represents mass, Volume is strictly linearly proportional to Mass number.

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Class 12 Physics: Nuclei

Q60 jee_main_2024_31_jan_morning Mass Defect And Energy
The mass defect in a particular reaction is 0.4 g. The amount of energy liberated is n × 10⁷ kWh where n = _______. (speed of light = 3 × 10⁸ m/s)
Numerical Answer. Answer: 1 to 1

Solution

Related Formula
E = Δ m c² 1 kWh = 3.6 × 10⁶ J
Core Logic

Given the mass defect:

Δ m = 0.4 g = 0.4 × 10⁻³ kg

The total energy liberated in Joules is:

E = (0.4 × 10⁻³) × (3 × 10⁸)² E = 0.4 × 10⁻³ × 9 × 10¹⁶ E = 3.6 × 10¹³ J
Step 2: Conversion to kWh

We need the answer in kWh. Since 1 kWh = 1000 W × 3600 s = 3.6 × 10⁶ J:

E = 3.6 × 10¹³3.6 × 10⁶ kWh E = 10⁷ kWh

Comparing this to n × 10⁷ kWh, we get: n = 1

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Class 12 Physics: Nuclei

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