Answer:
The process that explains why the bright side must face food is a process called Wave Reflection.
Step-by-step explanation:
The shiny side of foil should face the food because that side is able to reflect the heat waves with more intensity. That way the cooking will be faster than if the dull side was facing the food.
In addition, this shiny side, because it is smoother and less adherent, prevents food from sticking to its surface, keeping that texture irresistible from baked foods.