An atom is modelled by a stationary central positive point charge +Q surrounded by a spherical electron cloud (radius R , total charge of -Q ) of uniform charge density. The electron cloud is displaced slightly from its equilibrium position and released. Assuming that the cloud maintains its shape, select the correct statement(s) from the following options.

Options

1. AThe frequency of oscillation of electron cloud around positive charge is proportional to R^ -3 / 2 .
2. BThe force due to electron cloud on positive charge is inversely proportional to R^3 .
3. CThe frequency of oscillation of electron cloud around positive charge is inversely proportional to R .
4. DThe motion of displaced electron cloud is periodic but not simple harmonic.