Microwaves generally do not affect food inside other containers because microwaves operate on a principle called selective heating. This principle is based on the interaction between microwaves and water molecules, which are present in most foods.
Here's an explanation of why microwaves do not significantly affect food inside other containers:
Microwaves and water molecules: Microwaves emit electromagnetic waves that have a specific frequency range. When these waves encounter water molecules, they cause the molecules to vibrate rapidly, generating heat. Other molecules, such as those found in most food containers, do not readily absorb microwave energy in the same way as water molecules.
Non-reactive materials: Microwave-safe containers are made from materials that are transparent to microwaves and do not absorb or react significantly with the microwave energy. They allow the microwaves to pass through them and reach the food, while minimizing any potential interactions between the container and the microwaves.
Wave penetration: Microwaves are able to penetrate most non-metallic containers and reach the food within. This is why microwavable dishes are typically made of materials like glass, ceramic, or microwave-safe plastics, which do not interfere with the microwaves' ability to penetrate and heat the food.
Reflection and shielding: Metallic materials reflect microwaves rather than allowing them to pass through. This is why metal containers or those with metallic accents should not be used in a microwave, as they can cause sparks or potentially damage the microwave. However, it's worth noting that some microwaves have a metal rack or turntable, but these are specially designed to allow microwaves to pass through without causing arcing.
In summary, microwaves primarily interact with water molecules, causing them to vibrate and generate heat. Most food containers are made of materials that are transparent to microwaves, allowing the microwaves to pass through and heat the food inside while minimizing any effects on the container itself. Metallic materials, however, can reflect microwaves and should not be used in the microwave.