Question

The fact about tyndall effect is

• A. the diameter of dispersed particles is much smaller than the wave length of light used
• B. refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude
• C. it is shown by true solution
• D. All of the above

Answer 1

The correct option is B refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude

Tyndall, in 1869, observed that if a strong beam of light is passed through a colloidal sol placed in a dark place, the path of the beam gets lluminated. This phenomenon is called Tyndall effect, which is due to the scattering of light by the colloidal particles. The illuminated path of beam is called Tyndall cone. This phenomenon is due to scattering of light from the surface of colloidal particles. In a true solution there are no particles of sufficiently large diameter to scatter light & hence the beam is invisible.

Tyndall effect is light scattering by particles in a colloid or particles in a fine suspension. It is shown by colloidal solutions only.
Tyndall effect is observed only when
1. the diameter of dispersed particles is not much smaller than wavelength of light used.
2. the refractive indices of dispersed medium and dispersed phase must differ greatly.