Incorrect statement for Tyndall effect is :-
- (A)The refractive indices of the dispersed phase and the dispersion medium differ greatly in magnitude.
- (B)The diameter of the dispersed particles is much smaller than the wavelength of the light used.✓ Correct
- (C)During projection of movies in the cinemas hall, Tyndall effect is noticed.
- (D)It is used to distinguish a true solution from a colloidal solution.
Answer: (B)
Solution
The Tyndall effect occurs when light is scattered by colloidal particles. For this effect to be observed, the diameter of the dispersed particles should be comparable to or somewhat smaller than the wavelength of light used (typically in the range of 1-1000 nm).
Statement (B) is incorrect because it says the diameter is "much smaller" than the wavelength. If particles were much smaller than the wavelength, they would not scatter light effectively and the Tyndall effect would not be observed.
All other statements are correct: (A) refractive index difference is necessary for scattering, (C) cinema projection shows Tyndall effect through dust particles in air, and (D) it distinguishes colloidal solutions from true solutions.
Statement (B) is incorrect because it says the diameter is "much smaller" than the wavelength. If particles were much smaller than the wavelength, they would not scatter light effectively and the Tyndall effect would not be observed.
All other statements are correct: (A) refractive index difference is necessary for scattering, (C) cinema projection shows Tyndall effect through dust particles in air, and (D) it distinguishes colloidal solutions from true solutions.
JEE Main · 2022 · 25 Jun 2022 · Shift 1 · Single correct option