Oil and water are both transparent however, they lose their transparency once they are mixed together. What is the reason for this? The size of the molecules are still the same so why does the substance become cloudy?
Although the size of the molecules are still the same, the oil (nonpolar) cannot dissolve into the water (polar), so the oil drops form inside water, which is much larger than the molecule itself. Those drops (emulsion) reflects light and causes tyndall effect.