Tyndall effect is observed only when(i) the diameter of the dispersed ...
Tyndall effect is the phenomenon in which light is scattered by colloidal particles or suspended particles in a transparent medium, resulting in the visibility of a beam of light passing through the medium. This effect is observed when certain conditions are met:
(i) The diameter of the dispersed particles is not much smaller than the wavelength of the light used.
(ii) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.
Let's understand why option D is the correct answer:
(i) The diameter of the dispersed particles is not much smaller than the wavelength of the light used.
When the diameter of the dispersed particles is comparable to the wavelength of the light, scattering of light occurs. This scattering is responsible for the visible beam of light in the Tyndall effect. If the particles are too small compared to the wavelength of light, scattering is minimal, and the Tyndall effect is not observed. Therefore, condition (i) is necessary for the Tyndall effect to occur.
(ii) The refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.
The difference in refractive indices between the dispersed phase and dispersion medium is responsible for the scattering of light. When there is a significant difference in refractive indices, the light gets scattered by the particles, making the beam of light visible. If the refractive indices are similar, the scattering is minimal, and the Tyndall effect is not observed. Therefore, condition (ii) is necessary for the Tyndall effect to occur.
Considering the above explanations, option D is the correct answer as it includes both conditions (i) and (ii), which are necessary for the observation of the Tyndall effect. Option D correctly states that the Tyndall effect is observed when the diameter of the dispersed particles is not much smaller than the wavelength of the light used (condition i) and when the refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude (condition ii).
Tyndall effect is observed only when(i) the diameter of the dispersed ...
The phenomenon of scattering of light by colloidal particles as a result of which the path of the beam becomes visible is called a tyndall effect. Size of colloidal particles may range from 1 to 1000 nm.
Tyndall effect is observed only when the following conditions are satisfied:-
(i) The diameter of the dispersed particles is not much smaller than the wavelength of the light used.
(ii) The refractive indices of dispersed phase and dispersion medium differ greatly in magnitude. if the refractive indices of the dispersed phase and dispersion medium are almost similar in magnitude, then there will be no scattering of light and hence, therefore, no tyndall effect is observed.