I'm not sure fresnel is the right term. What GP referred to is probably iridescence [0].

[0] https://en.wikipedia.org/wiki/Iridescence

Yeah, he didn't call the color effect fresnel. He called the reflections fresnel. You're right that the color effect is called iridescence.

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

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

If you want to know lots about how materials interact with light to look the way they do, including how the Fresnel effect contributes, there was a great talk at the Blender conference this morning about it.

https://youtu.be/DQeP363Xmn4

The fresnel lens/effect is used in a number of places

- Those "invisibility shields" you see videos of

- In (vision) glasses, to correct for double vision (you can get prism in the glasses or, if the double vision is too much for that, a sticky "fresnel" lens that gets attached to the glass. I have one setting on my desk that I was using before my corrective surgery, actually... woo, tangents)

Augustin-Jean Fresnel was an engineer and physicist who made major contributions to the field of optics. As a result, many different things are named after him.

I am more familiar with "Fresnel" being a shading technique responsible for "rim lighting" in computer graphics, that's because this is an application of Fresnel equations, discovered by Fresnel. But in other fields, "Fresnel" can mean something else entirely, with the only thing in common being that it can be traced back to the work of Fresnel.