Question

Which of the following statements is true about the Tyndall effect?

• A. It is observed only when the size of the particles is generally between $10-11$ and$10-9m$in diameter.
• B. It is observed only when the refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.
• C. It is observed only when the diameter of the dispersed particles is not much smaller than the wavelength of the light used.
• D. Both (B) and (C)

Answer 1

The correct option is D

Both (B) and (C)

Explanation for the correct option:

(D) Both (B) and (C)

• It includes both the correct statements about the Tyndall effect.
• (B)It is observed only when the refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.
• This statement is true because the scattering of light in the Tyndall effect can happen only when the refractive indices of the dispersion phase and dispersion medium differ greatly, which allows more bending of light when light passes through the solution.
• Large bending of light rays in different directions leads to scattering of light and the Tyndall effect can be observed.
• Thus, it is a correct statement.
• (C)It is observed only when the diameter of the dispersed particles is not much smaller than the wavelength of the light used.
• This statement is correct because if the diameter of the particles is much smaller than the wavelength of light, then the dispersed particles would not be able to scatter the light incident on them and the light will pass through the solution unscattered without disturbing the particles of the solution.
• The relative length of the diameter of particles and the wavelength of light allows them to interact which further helps in the scattering of light and thus, the Tyndall effect is observed.
• Thus, it is a correct statement.

So, option(D) is the correct .

Explanation for the incorrect options:

(A)It is observed only when the size of the particles is generally between $10-11$ and$10-9m$in diameter.

• This statement is incorrect because for the Tyndall effect to occur, the size of the dispersed particles should be in the colloidal range that is, $1nm-1000nm$.
• Otherwise, the particles would not be able to scatter the light due to unrelative size with the wavelength of light used.

So, option(A) is incorrect.

(B)It is observed only when the refractive indices of the dispersed phase and dispersion medium differ greatly in magnitude.

• This statement is true because the scattering of light in the Tyndall effect can happen only when the refractive indices of the dispersion phase and dispersion medium differ greatly, which allows more bending of light when light passes through the solution.
• But, option(C) is also correct.
• So, it can not be the answer.

So, option(B) is incorrect.

Hence, option(D) is the correct answer, because it includes all the correct statements regarding the Tyndall effect.