Brownian motion is a random motion of particles present in the fluid such as air or liquid.This motion of the particles is due to collision with fast moving molecules in a fluid.
In colloids , molecules of dispersed phase are in motion due to the fast motion of dispersion medium's particle which imparts motion to these particles of dispersed phase by means of collision.
They are so small that they barely make up any of the mass of the atom, and they are so miniscule that during Rutherford 's Gold foil experiment ,they didn't even react with the alpha particles. They circle the nucleus on a ring. shown through Rutherford Atomic Model
The correct answer is the fourth option. The nervous system is the system in the body which can be affected by ionizing radiation. Exposure to this kind of radiation may lead to changes in motor function or neurological disorders.
