Microwaves interact differently with glass and ceramic containers compared to metal containers due to the properties of the materials and the behavior of microwaves.
Microwaves are electromagnetic waves that have the ability to excite water molecules, causing them to vibrate and generate heat. When microwaves pass through glass or ceramic containers, they do not directly interact with the material itself because glass and ceramic are transparent to microwaves. Instead, the microwaves pass through the container and interact with the water molecules present in the food.
In contrast, metal containers reflect microwaves rather than allowing them to pass through. When microwaves encounter a metal container, the metal acts as a barrier, preventing the microwaves from penetrating the container and reaching the food. The metal surface of the container reflects the microwaves, causing them to bounce off and potentially damage the microwave oven or create arcing (sparks) inside.
Additionally, the shape and design of metal containers can also contribute to the inability of microwaves to heat food effectively. Sharp edges or thin metal parts can lead to concentration of electric fields, which can cause sparking and potential damage to the microwave.
It's important to note that some microwave ovens have a "microwave-safe" label on certain metal containers. These containers are designed with specific coatings or materials that prevent arcing and sparking. However, it is generally recommended to use microwave-safe glass, ceramic, or microwave-safe plastics for optimal and safe microwave cooking.