Quantum Oil Slicks?

I had asked a psychology professor at my school whether he had read a certain book about quantum indeterminancy and free will. In his response he said:

Is this just a random stupid comment or is there something about our perception of colors in oil slicks (presumably those rainbow-colored type patterns) that involves quantum properties?

I tried searching threads to no availa and didn’t get anything on google either (wrong search terms?)

Is there anything to this is no?

I don’t believe the colors in oil slicks are a direct result of quantum effects (any more than everything is a result of quantum effects…). They’re a result of thin film interference.

Pretty much every intro to optics discusses the subject. A quick google search turned plenty of links including:

Basically, the color patterns are based on interference between reflected light waves. Interference is a basic property of wave interactions. It has nothing to do with quantum anything, really.

I think that your professor may have been referring to an example used by Richard Feynman in his lectures on quantum electrodynamics (QED for short). Classical physics treats light as a wave giving rise to phenomena such as interference, as stated in the replies above. QED however paints a different picture in which light is made from discreet particles called photons. Instead of thin film interference QED deals with the probability of individual photons being reflected from the upper and lower surfaces of the oil slick. Probability of reflection depends on the film thickness, and for a given thickness the colour of photon being reflected. Since white light is made up of all colours many different combinations are possible, giving the pretty patterns that are familiar when observing such thin films.

This link goes into greater detail:


Hope this helps :slight_smile:

P.S : The above replies are NOT wrong, but simply another way (classical) of explaining the phenomenon of iridescence.

Believe you’re right, NiNjAmAn (and welcome to the boards BTW!) I have Feymnam’s book “QED: The Strange Theory of Light and Matter,” which actually has an iridescent oil slick featured on the front cover.

The slim little book explains it all without very much math, and only in the last chapter starts getting kindof hairy and complicated.

*Originally posted by drewbert *
which actually has an iridescent oil slick featured on the front cover.

Er, pictured on the cover. The book isn’t all oily, that would be, uh… kinda gross.

Indeed, one can use QED to explain all electrodynamical effects… that’s what makes it a good theory.

However, oil slicks have been explained right and good by wave mechanics of light passing through refracting materials of varying thicknesses classically! No real need for quantum mechanics, per se.

The interesting thing is that if you ASSUME light is a particle, than to explain the effects of light as a wave (oil slicks, diffraction, etc) you must USE concepts of quantum electrodynamics as per outlined by Feynman (specifically the odd behavior of quantum particles that react with certain probabilities as INTRINSIC[!] to their identities).

It is really a case of establishing an quantum explanation for classical behavior.

What if the situation is more like the double-slit experiment in which classical waves seem to work until you get way down low and it stops being so easy?