Option (iii) is correct. Air with dust particles and starch with water show the Tyndall effect because their dispersed particles scatter light, making the path of the light beam clearly visible to the observer nearby.
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Option (IV) is correct. Muddy water, milk and blood are heterogeneous mixtures, while brass is a homogeneous mixture because its components are uniformly distributed throughout the mixture as distinct phases in all parts of it.
Bright rays of sunlight become visible when light passes through small gaps between leaves because dust and smoke particles in the air scatter the light. This scattering makes the path of the light beam visible.
Evaporation is a surface phenomenon in which liquid changes into vapour from its surface below the boiling point. Boiling occurs throughout the liquid at its boiling point and produces vapour rapidly throughout it.
Suspended particles in muddy water are larger and heavier, so they settle at the bottom with time. Milk contains much smaller colloidal particles that remain uniformly dispersed and do not settle easily when left undisturbed.