Question #3adf4
1 Answer
Soap foams are white because they scatter the light.
Explanation:
Reason 1. Dilute dyes
The coloured dyes in soaps and shampoos are highly diluted.
When we make a soap lather, an extremely small amount of dye goes into each bubble.
Reason 2. Thin bubbles
The film in each bubble is extremely thin (10 nm to 1000 nm).
This also limits the amount of colour in the bubble.
Reason 3. Scattering of light
This is probably the most important reason.
White light is a combination of visible light of different wavelengths.
Soap foam is a large collection of tiny soap bubbles.
Each bubble is mostly transparent, but there are many small bubbles.
Light entering the foam must pass through many bubbles, i.e., a number of surfaces.
These surfaces break the light into different colours and scatter the rays in all directions, so the foam looks white.
