Question

Tyndall effect is observed only when:
(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.
(iii) the size of the particles is generally between ${10}^{-11}$ and ${10}^{-9}$ m in diameter.
(iv) the dispersed phase and dispersion medium can be seen separately in the system.

• A. (i) and (iii)
• B. (i) and (iv)
• C. (ii) and (iii)
• D. (i) and (ii)

Answer 1

Answer: (D)

(i) and (ii)

• The Tyndall effect is the scattering of light as a light beam passes through a colloid.
  
• The Tyndall effect is due to the fact that colloidal particles scatter light in all directions in space. This scattering of light illuminates the path of the beam in the colloidal dispersion.

Tyndall effect is observed only when the following two conditions are satisfied.

• The diameter of the dispersed particles is not much smaller than the wavelength of the light used and
  
• The refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude.