Thin Film Interference | Observing Puddles of Oil on Pavement

AI Thread Summary
Thin film interference in oil puddles creates swirling colors, which appear more prominently on overcast days compared to sunny ones. The discussion explores whether diffuse light enhances this phenomenon more than direct light or if the angle of incidence plays a significant role. Additionally, the presence of a thin layer of water beneath the oil may introduce extra reflective boundaries, affecting the observed colors. It is suggested that bright sunlight might overpower the colors due to strong reflections at the oil-air interface. Overall, the interplay of light conditions and surface layers influences the visibility of thin film interference effects.
cepheid
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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?
 
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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.
 
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