Since the beginning of the Covid-19 pandemic, washing hands has become as common as leaving the footwears at the doorstep. But have you ever wondered why the color of the foam produced is white irrespective of the color of the soap? There are two main reasons. Firstly, the colorants that are added in the soap are of small proportion, as large proportion of it would stain the hands. The second reason seems quite interesting. The foam is formed due to the combined effect of soap liquid, air and water. The surface tension is responsible for obtaining the shape of the bubble. The bubble is completely transparent and acts as a mirror reflecting the light that is present in the surrounding. Since most of the light in the surrounding is white light, the phenomena of scattering of light comes into play and we tend to see white foam. So, we see the foam to be red in color when we expose the foam to red light.
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