Question

Tyndall effect is not observed in
A) Smoke
B) Emulsions
C) Sugar solution
D) Gold sol

Answer 1

Hint: The scattering of light by particles in its path is called the Tyndall effect. When a beam of sunlight enters a dusty room through a window then its path becomes visible to us.

Complete step-by-step answer:
Smoke shows the Tyndall effect since it is colloid, called aerosol which contains solid particles in gas and solid particles disperse a beam of light.
The term Tyndall effect is generally applied with the effect of light scattering on particles in colloid systems, for example, suspensions or emulsions. Since colloids have particles in them which scatter the passed light, they show Tyndall impact.
The sugar solution is a true solution and not a colloid solution. Hence, the Tyndall effect is not shown by the sugar solution.
A gold sol may contain particles of various sizes composed of several atoms of gold and so it is called a multimolecular sol. As gold sol is a colloid so it shows the Tyndall effect.

Hence the correct option is C.

Additional Information:
Smoke is a type of 'aerosol' colloid in which the dispersed medium is 'Gas' and the dispersed phase is 'Solid'.
A colloidal solution is a heterogeneous mixture in which the solute particles of around 1-100 nm in size are dispersed in the solvent.
A true solution is a homogeneous solution in which the solute particles have diameters between 0.1 nm to 1 nm i.e., the solute particles are of molecular dimensions.

Note: The possibility to make a mistake is that you may choose option A. But smoke is a colloidal solution, not a true solution, hence it shows the Tyndall effect.