JEE Main 2021 — Surface Chemistry Question with Solution
From: JEE Main 2021 (Online) 20th July Morning Shift
Question
The conditions given below are in the context of observing Tyndall effect in colloidal solutions :
(A) The diameter of the colloidal particles is comparable to the wavelength of light used.
(B) The diameter of the colloidal particles is much smaller than the wavelength of light used.
(C) The diameter of the colloidal particles is much larger than the wavelength of light used.
(D) The refractive indices of the dispersed phase and the dispersion medium are comparable.
(E) The dispersed phase has a very different refractive index from the dispersion medium.
Choose the most appropriate conditions from the options given below :
(A) The diameter of the colloidal particles is comparable to the wavelength of light used.
(B) The diameter of the colloidal particles is much smaller than the wavelength of light used.
(C) The diameter of the colloidal particles is much larger than the wavelength of light used.
(D) The refractive indices of the dispersed phase and the dispersion medium are comparable.
(E) The dispersed phase has a very different refractive index from the dispersion medium.
Choose the most appropriate conditions from the options given below :
Choose an option
Show full solutionCorrect option: A
Correct answer
A(A) and (E) only
Step-by-step explanation
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. Smaller the diameter and similar the magnitude
of refractive indices, lesser is the scattering and hence the tyndall effect and viced-versa. The
diameter of the dispersed phase particle should not be smaller than the wavelength of light
used because they won't be able to scatter the light so, therefore, the diameter of the dispersed
particles should be equal or not much smaller than the wavelength of the light used.
2. The refractive indies (i.e. the ratio of the velocity of light in vacuum to the velocity of light in any medium) of the dispersed phase and the dispersion medium should differ greatly in magnitude than only the particles will be able to scatter the light and tyndall effect will be obersved. On the other hand, 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 effect is observed.
Hence answer (A) and (E) are correct.
2. The refractive indies (i.e. the ratio of the velocity of light in vacuum to the velocity of light in any medium) of the dispersed phase and the dispersion medium should differ greatly in magnitude than only the particles will be able to scatter the light and tyndall effect will be obersved. On the other hand, 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 effect is observed.
Hence answer (A) and (E) are correct.
Practice this on the real CBT interface
Solve this JEE Main question (and the rest of the Surface Chemistry chapter) on PrepSharp's TCS iON-style CBT player — with timer, bookmarks and session analytics.
Solve interactively →About this question
This is a previous-year question from JEE Main 2021, covering the Surface Chemistry chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.