COLOURS IN BUBLLES

Children love to play with soap bubbles. The feel, colours, and motion attracts them. Let us see how the colours appear in the bubbles.

It is a hollow sphere made up of thin film of water. Only air is inside the bubble. We know the sunlight contains the famous seven colours. The sunlight enter and exit the bubble. There may be several reflected and refracted rays of sunlight in the water film.

At one point in the bubble, the thickness of the film and our viewing angle may be such that; only red light waves(rays) will be in phase (in order); then they will reinforce themselves and red will appear bright in that point. All other colour waves will be out of phase (in disorder) and they will destroy themselves at that point.

By the same reasoning we can tell, at another point yellow will only appear; at the next point only orange will be bright. So one by one all the colours in the sunlight appear in the bubble. In physics, this phenomenon is called interference of light.

Interference is also the reason for the appearance of colours in oil film floating on water; in CD; in DVD.

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