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JEE Advanced · Physics · 28. Nuclear Physics

The electrostatic energy of Z protons uniformly distributed throughout a spherical nucleus of radius R is given by E=35ZZ-1e24πε0R The measured masses of the neutron, H11, O815 are 1.008665 u, 1.007825 u, 15.000109 u and 15.003065 u respectively. Given that the radii of both the N715 and O815 nuclei are same, 1u = 931.5 Me V/ c2 (c is the speed of light) and e24πϵ0=1.44 MeV fm. Assuming that the difference between the binding energies of N715 and O815 is purely due to the electrostatic energy, the radius of either of the nuclei is 1 fm=10-15m

  1. A 2.85 fm
  2. B 3.03 fm
  3. C 3.42 fm
  4. D 3.80 fm
Verified Solution

Answer & Solution

Correct Answer

(C) 3.42 fm

Step-by-step Solution

Detailed explanation

Electrostatic energy \(=B E_N-B E_O\)
\(=\left[\left[7 M_H+8 M_n-M_N\right]-\left[8 M_H+7 M_n-M_O\right]\right]\) \(\times ~C^2 \)
\( =\left[-M_H+M_n+M_O-M_N\right] C^2 \)
\( =[-1.007825+1.008665+15.003065\) \(-~15.000109] \times 931.5 \)
\( =+3.5359 MeV \)
\( \Delta E=\frac{3}{5} \times \frac{1.44 \times 8 \times 7}{R}-\frac{3}{5} \times \frac{1.44 \times 7 \times 6}{R}=3.5359 \)
\( R=\frac{3 \times 1.44 \times 14}{5 \times 3.5359}=3.42 fm\)
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