MCQMediumJEE 2023Atomic Mass & Binding Energy

JEE Physics 2023 Question with Solution

For a nucleus ZAX^A_ZX having mass number AA and atomic number ZZ:

Options:

  • A

    B, C only

  • B

    A, B, C, D only

  • C

    B, C, E only

  • D

    C, D only

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: A nucleus ZAX^A_ZX has mass number AA and atomic number ZZ.

Find: Which listed statements are correct based on the binding energy equation.

The solution provides the binding energy relation:

EB=avAasA2/3acZ(Z1)A1/3aa(A2Z)2A+δ(A,Z)E_B = a_v A - a_s A^{2/3} - a_c \frac{Z(Z-1)}{A^{1/3}} - a_a \frac{(A-2Z)^2}{A} + \delta(A, Z)

From this equation:

  • Volume term is avAa_v A
  • Surface energy term is asA2/3-a_s A^{2/3}
  • Coulomb term is acZ(Z1)A1/3-a_c \frac{Z(Z-1)}{A^{1/3}}
  • Asymmetry term is aa(A2Z)2A-a_a \frac{(A-2Z)^2}{A}
  • Pairing term is δ(A,Z)\delta(A, Z)

The extracted solution explicitly states that C and D are directly supported by the equation.

Therefore, the correct option is D.

Using the extracted explanation

Given: The question concerns the semi-empirical mass formula for nuclear binding energy.

Find: Which combination of statements matches the equation.

The hint says that the binding energy equation is essential to understand nuclear stability. The provided explanation analyzes each term of

EB=avAasA2/3acZ(Z1)A1/3aa(A2Z)2A+δ(A,Z)E_B = a_v A - a_s A^{2/3} - a_c \frac{Z(Z-1)}{A^{1/3}} - a_a \frac{(A-2Z)^2}{A} + \delta(A, Z)

Then it matches the statements with the formula and concludes that only C and D are supported.

Since the options are:

  • A: B, C only
  • B: A, B, C, D only
  • C: B, C, E only
  • D: C, D only

The correct option is D.

Common mistakes

  • Students often confuse the surface term with the volume term. This is wrong because the formula contains different powers of AA for these contributions. Always identify each term directly from the exponent of AA in the binding energy equation.

  • A common mistake is to ignore the negative signs in the Coulomb and asymmetry terms. This is incorrect because these terms reduce the binding energy. Always track the sign of each contribution before matching statements.

  • Some students rely on the final option number written in the explanation without checking consistency. Here the text says option (3)(3), but the extracted reasoning supports C and D, and the given correct answer maps to option D. Always verify the statement combination against the option list.

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