The ratio of the radii of two nuclei of mass numbers $A_1$ and $A_2$ respectively would be

$(A_1/A_2)^{1/3}$

The correct answer is Option (4) → $(A_1/A_2)^{1/3}$

Formula:

The radius of a nucleus is given by

$R = R_0 A^{1/3}$

where $R_0$ is a constant and $A$ is the mass number.

Therefore, the ratio of the radii of two nuclei is

$\frac{R_1}{R_2} = \left( \frac{A_1}{A_2} \right)^{1/3}$

Hence, $\displaystyle \frac{R_1}{R_2} = \left( \frac{A_1}{A_2} \right)^{1/3}$