Microondes

Microondes, or microwaves, refer to a region of the electromagnetic spectrum with frequencies roughly from 1 gigahertz to 300 gigahertz, corresponding to wavelengths from about 30 centimeters to 1 millimeter. They are non-ionizing radiation and can heat materials containing polar molecules, a principle exploited in microwave heating and cooking as well as in industrial processing.

Properties of microwaves vary with frequency and material. Metals strongly reflect microwaves, while dielectric materials may absorb, transmit, or partially reflect them depending on their properties. Microwaves interact with matter primarily through dielectric heating, causing polar molecules like water to rotate and generate heat. Penetration depth depends on frequency and the material, influencing applications in cooking, imaging, and communications.

Technology and devices: Microwave energy is produced by devices such as magnetrons, klystrons, traveling-wave tubes, and solid-state sources, and is guided by waveguides or coaxial lines. The 2.45 gigahertz frequency is standard for domestic microwave ovens, while higher-frequency bands are used for radar, satellite links, and various wireless communications, including millimeter-wave technologies in some 5G networks.

Applications: In cooking, microwave ovens heat food by dielectric heating. In communications, microwaves enable line-of-sight links for satellite communication, terrestrial backhaul, and certain wireless networks. In science and industry, microwaves are used for radar, remote sensing, spectroscopy, and dielectric heating of materials.

Safety: Microwave radiation is non-ionizing but can cause heating and tissue damage with intense exposure. Regulations set exposure limits, and devices employ shielding and interlocks to minimize leakage.

History: The practical use of microwaves developed in the 1930s–1940s, with the cavity magnetron playing a crucial role in radar and later in communications and cooking technologies.