Question
  1. In a typical nuclear reaction, e.g.
$^{2}_{1}\text{H} +^{2}_{1}\text{H}\rightarrow^{3}_{2}\text{He} + \text{n} + 3.27\text{MeV}$

although number of nucleons is conserved, yet energy is released. How? Explain.
  1. Show that nuclear density in a given nucleus is independent of mass number A.

Answer

  1. In nuclear reaction
$^{2}_{1}\text{H} +^{2}_{1}\text{H}\rightarrow^{3}_{2}\text{He} + \text{n} + 3.27\text{MeV}$

Cause of the energy released:
  1. Binding energy per nucleon of$^{3}_{2}\text{ He}$ becomes more than the (BE/A) of $^{2}_{1}\text{ H}.$
  2. Mass defect between the reactant and product nuclei.
$\Delta\text{E} = \Delta\text{mC}^{2}$

$ = \big[2\text{m}(^{2}_{1}\text{H}) - \text{m}(^{3}_{2}\text{He}) + \text{m}(\text{n})\big]\text{C}^{2}$
  1. The radius of nucleus of mass number A is given by $R = R_0A^{1/3}$
Volume of the nucleus $\text{V} = \frac{4}{3}\pi\text{R}^{3} = \frac{4}{3}\pi\text{R}_{0}^{3}\text{A}$

Density of the matter in the nucleus

$\rho = \frac{\text{Mass}}{\text{Volume}} = \frac{\text{A}{(u)}}{\frac{4}{3}\pi\text{R}_{0}^{3}\text{A}}$

$\rho = \frac{1}{\frac{4}{3}\pi\text{R}_{0}^{3}} = \frac{3}{4\pi\text{R}_{0}^{3}}$

The expression of the density is independent of mass number A.

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