Mirage
An optical illusion caused by continuous refraction of light rays passing through air layers with steep temperature and density gradients.
Governing formula
n(z) = f(Temperature gradient)
SI unit
N/A
In depth
Hot ground heats adjacent air, lowering its density and refractive index. Light rays from the sky bend upward into the observer's eye, creating a virtual reflection resembling water.
Examples in the real world
Inferior mirages on desert sand or hot asphalt roads appearing as shimmering puddles of water.