We know that water is colourless. But once it starts falling from a height, it appears white. The reason is because water has oxygen dissolved in it, and when it falls from a height, the dissolved oxygen evaporates in the form of a gas. Consequently, millions of small water bubbles are formed. These little droplets of water act like millions of tiny mirrors that reflect light at different angles, in different directions.This is known as scattering of light. When light is scattered, it becomes white in colour, because of a phenomenon known as diffuse reflection. Diffuse reflection can also be seen when light strikes an irregular surface of a clear substance like glass, such as frosted window, or the surface of a frosted light bulb.