Van der waals forces can best be described as the attractive or repulsive forces that are formed
here are the options:
a: between oppositely charged ions in a crystal.
b: during dipole-dipole interactions between molecules.
c: when molecules move apart in the absence of other forces.
d: by a random, short-lived redistribution of electrons.

it will be pushed away from the source of the electric field. a negative charge in a cloud induces a positive charge in the ground below the cloud.

explanation:

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.