When microwaves are not absorbed by food, they continue to propagate through the microwave oven cavity until they encounter an object that can absorb them. In a microwave oven, the microwaves are generated by the magnetron, and they bounce around the oven chamber in all directions.
Here's what happens to the microwaves when they are not absorbed by food:
Reflection: Some of the microwaves may reflect off the walls, ceiling, and floor of the microwave oven. Microwave ovens are designed with reflective metal surfaces to help contain and distribute the microwaves effectively.
Absorption by other materials: If there are other objects inside the microwave oven, such as a microwave-safe container or a microwaveable plate, some of the microwaves may be absorbed by these objects.
Scattering: Microwaves can scatter when they encounter irregular surfaces or objects with different densities. This scattering can lead to a more even distribution of the microwave energy within the oven.
Leakage: Modern microwave ovens are designed to have minimal microwave leakage, ensuring that most of the microwaves stay inside the oven cavity. However, a small amount of leakage might occur, and this is why it's essential to have a well-maintained and functioning microwave with a properly sealing door.
Interference patterns: When microwaves bounce off surfaces and encounter each other, they can create interference patterns, leading to regions of constructive and destructive interference. This can affect the distribution of the microwave energy inside the oven.
In summary, when microwaves are not absorbed by food, they interact with various objects and surfaces inside the microwave oven, leading to scattering, reflection, and possibly some absorption. The design of the microwave oven ensures that the majority of the microwave energy remains inside the oven cavity to cook the food effectively and safely.