Question

Assertion : Colours are seen in thin layers of oil on the surface of water.
Reason : White light is composed of several colours.

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

Answer 1

Answer: (B)

Colours are seen in thin layer of oil on the surface of water, because of interference of light. When white light falls on a thin film of a liquid it will appear bright having colour whose wavelength satisfies the relation 2 μt cos r = (2n + 1) $\lambda /2$. The colour of the film will depend upon the thickness of the film and the angle of refraction.