What causes changes in the colours of soap or | vedclass

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(C) The phenomenon of colours in thin films is due to the interference of light waves reflected from the top and bottom surfaces of the film.For a giv

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Thickness of film

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(C) The phenomenon of colours in thin films is due to the interference of light waves reflected from the top and bottom surfaces of the film.For a given beam of light, the path difference between the reflected waves depends on the thickness of the film $(t)$, the refractive index of the film $(\mu)$, and the angle of refraction $(r)$.The condition for constructive interference (bright fringe) is $2\mu t \cos(r) = (n + 1/2)\lambda$.Since the thickness $(t)$ of a soap or oil film is typically non-uniform, different parts of the film satisfy the condition for different wavelengths $(\lambda)$ of light.Therefore, the variation in the thickness of the film causes different colours to be observed at different points.

What causes changes in the colours of soap or oil films for a given beam of light?

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