Answer:
Explanation:
What occurs here (the description in the question) is condensation. Condensation is the process in which water changes from it's gaseous state (steam) to it's liquid state. When the hot air leaves the oven, and it touches/ passes through the glasses of John (that is of a lower thermal energy), the hot air would lose some of it's thermal energy (due to the lower thermal energy of the glasses) and then transits back to liquid forming the visible fog steam on the glasses.
