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

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

Explain the colour formation in a thin oil film.

What should be the order of the thickness of oil film on the water surface to enable one see the colour in it ?

Assertion: The colour of the oil film on the surface of water continuously changes. Reason: The colour of the light reflected by the oil film depends upon its thickness.

Colours of soap film in sun light is due to

Dark and colour patterns on thin soap films are due to-

What is the cause of change in direction of a ray of light on refraction?