Assertion :Colloidal sol scatter the beam of light while true solutions do not.
Reason :The particles in colloidal sol are bigger than those of true solutions.

Tyndall effect is, in fact, the definitive test to show the difference between a true and a colloidal solution. it works on the principle that light beams scatter due to the presence of large colloidal particles in the solution which separate the light however in a true solution the particles are not as large enough to scatter the light particles, that's why Tyndall effect is not seen in true solution.

Colloid particles are larger than water and large enough to show Tyndall effect.