Thin Film Interference | Observing Puddles of Oil on Pavement

[cepheid]

I have observed puddles of oil on the pavement with swirling colours more often on overcast days than sunny days. Does the phenonmenon of thin film interference work better with diffuse/scattered light than light coming directly from a source? Or, is it a question of light incident at an oblique angle rather than coming from directly overhead? OR, does it have less to do with the ambient lighting, and more to do with the rain, i.e. is there a thin layer of oil on top of a thin layer of water, adding additional reflective boundaries/optical media?

 

[Claude Bile]

It could be that the reflection from the oil-air interface is strong enough on a bright day to partially wash out the swirling colours.

Claude.

 

[astrokreng]

I can provide a response to your observations of thin film interference in puddles of oil on pavement. Thin film interference occurs when light passes through or reflects off of a thin layer of a material with a different refractive index than the surrounding medium. In the case of oil on pavement, the thin layer of oil has a different refractive index than the air above it and the pavement below it, causing interference effects.

To answer your question, the phenomenon of thin film interference is not dependent on the type of light (diffuse/scattered or direct) or the angle at which it is incident, but rather on the thickness and refractive index of the thin film itself. However, the appearance of the interference patterns may vary depending on the lighting conditions and angle of observation.

In the case of puddles of oil on pavement, the presence of rainwater can indeed contribute to the thin film interference. The thin layer of water on top of the oil creates an additional reflective boundary, adding to the interference effects. This can also explain why you may observe more pronounced interference patterns on overcast days, as rainwater is more likely to be present on the pavement.

In conclusion, the phenomenon of thin film interference is a result of the properties of the thin film and its interaction with light, rather than the lighting conditions or angle of observation. However, these factors can affect the appearance of the interference patterns. The presence of rainwater can also contribute to the interference effects in the case of oil puddles on pavement.