To find
The illusion of water on top of hot asphalt on a summary day is:
Explanation
Diffusion: It is a process of flow of molecules from a region of higher concentration to a region of lower concentration.
Mirage: It is an optical phenomenon where the incident light bends due to refraction and produce a displaced image of an distant object
An incident ray: The ray of light that falls on a surface
Conclusion
From the defintion it is clear that
The illusion of water on top of hot asphalt on a summary day is: a mirage