Question

The Tyndall effect is not observed in:
(A) suspensions
(B) emulsions
(C) colloidal solutions
(D) true solutions

Answer 1

Hint: Tyndall effect is related to the scattering of light by particles in a solution. So, from the given options identify the solution in which the size of solute particles is too small that it is not distinct from the solution. By this, Tyndall effect is not observed in the solution type and thus will give the correct answer.

Complete step by step answer:
The Tyndall effect is nothing but particles scattering the ray of light in a colloid or in a very fine suspension. It is also known by the name of Tyndall scattering.
Under Tyndall effect, the longer wavelengths are more transmitted while the shorter wavelengths get diffused easily via scattering. The Tyndall effect is seen or observed when light-scattering particulate matter is also dispersed in an otherwise light-transmitting medium. The diameter of the particles should be of the order of 40-900 nm i.e. roughly near the wavelengths of visible light(400-740 nm).
Tyndall effect is mainly applicable to colloidal mixtures and some suspensions having size of particles near the range of ideal particles. However, Tyndall effect is not observed in true solution as the diameter of particles is very small and hence cannot scatter light of significant measure.
So, the correct answer is “Option D”.

Note: Tyndall scattering is often considered synonymous with Rayleigh scattering. However, it is important to know that in case of Rayleigh scattering, the intensity of scattered light is inversely proportional to the fourth power of wavelength which is not observed in Tyndall scattering.