Why do these bubbles change colours before popping when they land in the wet patch on my driveway?
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The detergent is causing a refringent interference of light. Soap moves in a flat layer in the bubble and this causes different light wavelengths to reflect back, interfere with each other, making different colors.
Here's your physical explanation:
https://youtube.com/shorts/0JESoOp87yc
https://youtu.be/HG_dtNd53_4
Oil film...
Maybe not motor oil, but almost certainly some kind of fluid from a car that contains oil or an oil like substance.
Just the most likely explanation, if you wash your car in the driveway and this was the first rain, it could just be soap.
Im more interested in the physics as to why the colours flash. They dont do that when they land anywhere else. Just the wet spot.
What do you mean by flash?
If you mean like a firework, that's because the droplets of oil/whatever get flung out when the surface tension pops.
If you mean the color changes, as the bubble expands the amount of oil/film becomes thinner and that changes the color due to changing the density.
Like how there's a very narrow slice of eye color that has enough pigment density to be green when the pupil dilates, but when constricted there's not enough density due to increased surface area and they look blue.
(To be clear that is a very narrow slice and nowhere near the amount of people who claim their eyes fully change color)
The color depends on the thickness. It is based on which wavelengths multiple it is, so will cycle through the wavelengths repeatedly, i.e. through the colors, as the bubble gets thinner.
The liquid is probably flowing out of the bubble onto the ground in a slow controlled way, until the bubble gets too thin and pops.
You can also use color rings to tell how gravity and wind are pulling on bubbles, and adding fluid to them should also cycle through the colors. When you attach them to the dispense you can see liquid flow into the bubble.