Question

Which of the following will exhibit the Tyndall effect?

• A. Salt solution
• B. milk
• C. Copper (II) sulphate solution
• D. starch solution

Answer 1

Answer: (B), (D)

starch solution

Explanation for the correct options:

(B) Milk: Milk is an example of colloids and colloids show the Tyndall effect.

• A colloid is a heterogeneous mixture in which the particles cannot be seen with the naked eye.
• The diameter of the particles of colloids lies in the range of ${10}^{-6}-{10}^{-9}\mathrm{m}$.

Tyndall effect: When the particles can scatter a beam of light passing through them and make the path of light visible.

• The light is scattered when light collides with the colloidal particles and deviates from its normal straight line path.
• This scattering makes the path of the light beam visible, as illustrated below.

(D) Starch solution: Similar to the option (A), starch solution is also an example of colloid.

Explanation for the incorrect options:

(A) Salt solution: Solutions such as salt solution do not show the Tyndall effect as the size of particles $(<{10}^{-9}\mathrm{m})$ is so small that they cannot scatter the light.

(C) Copper (II) sulphate solution: Copper (II) sulphate $\left({\mathrm{CuSO}}_4\right)$ solution, similar to the option (A), does not show the Tyndall effect because of the small particle size of the solute.

Hence, options (B) and (D) are correct.