Consider the following nuclear reaction

$$ { }^{238} \mathrm{U} \longrightarrow{ }^{234} \mathrm{Th}+{ }^4 \mathrm{He} $$

Take masses of ${ }^{238} \mathrm{U},{ }^{234} \mathrm{Th}$ and ${ }^4 \mathrm{He}$ as $238.050 \mathrm{u}, 234.043 \mathrm{u}$ and 4.003 u , respectively. The $Q$ value for the reaction, in keV, is:

[Given: $1 \mathrm{u}=931.5 \mathrm{MeV} \mathrm{c}^{-2}$ ]

In Geiger-Marsden experiment, the number of scattered $\alpha$-particles $N(\theta)$ is plotted as a function of scattering angle $\theta$. Which of the following options represents the correct plot?

In the first excited state of hydrogen atom, the energy of its electron is -3.4 eV . The radial distance of the electron from the hydrogen nucleus in this case is approximately:

(Take $1 \mathrm{eV}=1.6 \times 10^{-19} \mathrm{~J}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$ and $\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \mathrm{~N} \mathrm{~m}^2 / \mathrm{C}^2$ )

Four statements are given ( $A$ is mass number):

A. The volume of a nucleus is proportional to $A^{1 / 3}$.

B. The volume of a nucleus is proportional to $A$.

C. The difference in mass of an atom and its nucleus is called the mass defect.

D. The difference in mass of a nucleus and its constituents is called the mass defect.

Choose the correct answer from the options given below: