Like the title says: when you see “heat rising” (the wavy/blurry area above a heat source), what are you actually seeing?
Bonus question: How does that cast a shadow? I noticed when I was opening my air fryer, I could see the shadow of the heat rising but, looking at the hot basket itself, couldn’t see it.
You are seeing changes in the refractive index of air as a result of heat lowering the density of the air. As air comes in contact with the hot surface, it becomes heated and rises through otherwise cool air - The rising air causes eddies and vortexes that lead to light bending in weird ways as it passes through.
The shadows are much like the shadows on the bottom of a pool when there are waves on the surface. Incoming wavefront of light are distorted from planar and sent in different directions, some directions get less total light, some get more.
Great explanation! The anology of the pool was helpful!
“wavefront of light”, “distorted from planar” 🤯
You took me straight back to a D- in intro to optics and modern physics where my classmates were trying to solve problems based on concepts, where I was trying to solve the problem of not understanding the concepts.
This video by Steve Mould shows this with wavey acrylic designed to project an image using caustics:
https://youtu.be/wk67eGXtbIw