Why is milk cloudy

Milk contains both organic and inorganic components. A majority of the milk is water based, and contains water-soluble solutes such as calcium compounds. But milk also contains as much as 15 per cent by mass of water-insoluble, fat-based compounds. 

But the microscopic fat particles suspended in milk have an average diameter in the range 10-7 to 10-5 m, i.e. much larger than k of visible light. A beam of incident light is scattered rather than transmitted by a suspension of particles - a phenomenon known as the Tyndall effect. 

In summary, milk appears cloudy because the suspended fat particles scatter any incident light. 

The continuous phase is said to be the dis-persAL medium (or phase), and the suspended particles are the dispersED medium (or phase). 

The study of the scattering of light by colloidal systems has a long history. The Tyndall effect describes the scattering of light by suspended particles. In fact, the first rigorous theory was that of Rayleigh in 1871. 

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