Why does milk look white?

Milk looks white because it contains tiny suspended particles of fat globules and proteins (casein) that scatter and reflect all wavelengths of visible light equally in all directions. Since no single wavelength is absorbed or transmitted, all colours of light get reflected back together — and when all colours of visible light are reflected simultaneously, our eyes perceive it as white. This is exactly the same reason why clouds, foam, and snow also appear white.

• Light Scattering: Fat globules and casein protein particles in milk scatter all wavelengths of visible light equally in all directions
• No Selective Absorption: Since milk reflects all wavelengths rather than absorbing any specific colour, the resulting mixture of all colours appears white to our eyes
• Colloidal Nature: Milk is a colloid — fat globules and casein particles suspended in water scatter all wavelengths of visible light equally, which is why it appears white and opaque unlike pure transparent water
• Comparison: Pure water is transparent because it has no suspended particles to scatter light — milk has particles, making it opaque and white
• Proteins and Sugars: While milk does contain proteins and sugars, these are not responsible for its white colour — it is the reflection and scattering of light that causes whiteness