Tyndall effect is more effectively shown by :

Solution

Chemistry ma’am · 3 steps

Scattering needs two things: particles of the right size and a big refractive-index gap with the medium.

1. Two conditions. A beam shows up as a bright path only when light is scattered. That needs particles not much smaller than the wavelength of light (colloidal size, 1 to 1000 nm). It also needs a large difference in refractive index between the particles and the medium.
2. Lyophobic versus lyophilic. Lyophobic particles do not attract the medium, so they stay distinct and their refractive index differs a lot from it. Lyophilic particles are heavily solvated, so their refractive index comes close to the medium's and scattering is weak.

   System	Particle size	Refractive index gap	Tyndall effect
   True solution	below 1 nm, too small	not relevant	absent
   Lyophilic colloid	colloidal	small (particles solvated)	weak
   Lyophobic colloid	colloidal	large	strong
   Suspension	above 1000 nm	not relevant	not shown; mixture is turbid and settles

3. So. Only the lyophobic colloid meets both conditions well, so it shows the Tyndall effect most effectively. The answer is (c).

The idea to keep. For Tyndall effect, check size first (it must be colloidal), then the refractive-index gap. Solvation shrinks the gap, so lyophilic sols scatter less than lyophobic ones.

Answer from the NTA final answer key. Solution by PrepWiser.