Question

why does the solution NaCl not show tyndall effect wherebthe mixture of milk shows

Answer 1

when the Nacl is mixed in water it gets totally dissolved in water and thus there is no particle to show Tyndall effect...but when there is mixture of milk the particles are colloidal and are in suspension in liquid thus the colloidal solution shows the tyndall effect.

Answer 2

NaCl solution shows Tyndall effect because there higher refractive index than milk. The second reason is that the solution is a mixture of 2 compounds whereas milk is not.