Microwaves ovens don't have metal cases because metal can indeed reflect microwaves very effectively, which would interfere with the cooking process. Instead, microwave ovens are designed with metal mesh or grid on the front window, but the rest of the casing is made from a specialized type of metal known as "microwave-safe metal."
Here are the main reasons why microwave ovens have metal components that are carefully engineered:
Safety: Microwave ovens use electromagnetic waves, specifically microwaves, to cook food. If the entire casing were made of metal, the microwaves would bounce around and create hotspots within the oven. This could lead to uneven cooking and potentially damage the oven itself, which could be hazardous.
Wave penetration: The metal mesh or grid on the front window of a microwave is designed to allow only a portion of the microwaves to pass through. This partial transparency ensures that you can see inside the microwave and monitor your food while preventing excessive microwave leakage.
Containment: Microwave ovens are designed to contain the microwaves within the cooking chamber. The metal casing, along with the metal grid on the window and a metal mesh on the back, prevents microwaves from escaping and potentially causing interference or harm to nearby electronic devices or people.
Reflecting microwaves within: The metal walls inside the microwave oven are specially coated to prevent reflection of microwaves. The interior is typically covered with a conductive material that helps absorb the microwaves, converting them into heat to cook the food.
In summary, microwave ovens are designed with specific metal components and coatings to ensure that microwaves are contained within the cooking chamber and efficiently absorbed to cook the food evenly and safely. This way, the metal parts of the microwave contribute to the cooking process without reflecting microwaves and causing interference or safety issues.