Fuel Spill Rainbow Colours

Prudie | 19:07 Tue 22nd Sep 2015 | Science

8 Answers

At work today there was a fuel spill on a wet tarmac road that I just had to stare at, so beautiful, An array of gold through pink,purple,blue and green. Please explain what causes this effect when I assume it's a clear fairly colourless liquid?

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gingejbee

....

https://www.quora.com/Gasoline/What-causes-the-rainbow-of-colors-to-appear-in-oil-spills-in-parking-lots

jomifl

diffraction

Sam1960

This any good Prudie.....

http://www.scientificamerican.com/article/why-do-beautiful-bands-of/

jomifl

https://en.wikipedia.org/wiki/Iridescence

Prudie

Question Author

The Scientific American article details the other bit of my question. Unlike soap bubbles (or do I mean diamonds), this spill held the colours in separate areas that did not change depending on where I was looking at it from. So it seems to be based on the thickness of the oil in relation to the water it was lying on giving different colours. I don't pretend to understand the wavelength physics.

Linotype

Hi there: Interesting phenomena that motorcyclists have known about for years! If you wear polaroid-type sunglasses when riding a motorcycle you enhance your chances considerably of spotting a diesel oil spill on the tarmac – you don't want to hit it because it can cause an "off". Remember there are only two types of motorcyclists: those who haven't fallen off yet, and those that are going to some time in the future! Seriously though, all it is is an oil streak lying on top of water, oil will always be uppermost ... Take care fellow bikers out there ...

Bert

I haven't looked at the links, so my remarks may be repeating what is in them. The phenomenon is due to "thin-film interference", not diffraction. The colours may seem to be similar to those in the rainbow, but they are not the same, as the colours you see in oil slicks are caused by mixtures of wavelengths, those wavelengths that happen to reinforce after reflection from the upper and lower surfaces of the oil. The colours in the rainbow are pure single wavelengths spread out from red to violet.
Re Linotype's suggestion that there are only two types of motorcyclists: his tow categories amount to the same thing. I think he means that the two types are those who have fallen off and those who haven't fallen off ... yet.