Question

why only colloids exhibit Tyndall effect?

Answer 1

Tyndall effect refers to the scattering of light by colloidal particles.  The intensity of the scattered light depends on the difference in the refactive indices of the dispersed phase and the dispersion medium. Larger the difference, greater will be the intensity of the scattered light.  In lyophobic sols, the particles are not as highly solvated as in lyophilic sols. So, the difference in refractive indices between the particles and the medium is quite large in lyophobic sols. Therefore, they show distinct Tyndall effect.

Answer 2

⭕️Remember that in true solutions, solute dissolves completely in the solvent.

⭕️The solute particles are present at their molecular size i.e. well below the size of a particle required to exhibit light scattering dispersion (the Tyndall effect).

⭕️the particles in colloids, in most true solutions, are large enough to scatter visible light.


⭕️In true solutions the size of the particles is too small to be seen by naked eye and too small for light to be scattered.

⭕️whereas in a colloidal solution the size of the particles is not so big to be seen individually by the naked eye .

⭕️colloidal sol is big enough to scatter light  and that's why it shows tyndall effect.