Microwaves are a form of electromagnetic (EM) radiation, which is a type of energy that travels in waves. Like all electromagnetic waves, microwaves can theoretically travel indefinitely through space if there are no obstructions or absorption effects. However, in practice, there are factors that limit how far microwaves can travel without significant attenuation or weakening of the signal.
The distance that microwaves can effectively travel before being significantly attenuated depends on their frequency and the surrounding environment. Generally, higher frequency microwaves (such as those used in microwave ovens) are more susceptible to absorption and scattering by atmospheric gases, rain, and other obstacles, so they have a shorter effective range compared to lower frequency microwaves.
For example, microwaves in the gigahertz frequency range, like those used in Wi-Fi networks (2.4 GHz or 5 GHz), typically have an indoor range of about 100 feet (30 meters) to 300 feet (90 meters) and an outdoor range of around 200 feet (60 meters) to 1000 feet (300 meters) with line-of-sight. However, their range can be reduced significantly if there are walls or other obstacles in the path of the waves.
On the other hand, microwaves used for long-distance communication, such as in microwave communication towers, typically operate at lower frequencies (e.g., 6 GHz to 30 GHz or even lower), which allows them to travel longer distances, potentially up to dozens of miles (over 50 kilometers) without significant attenuation.
In summary, the shortest distance that microwaves can effectively travel without being significantly attenuated depends on their frequency, the environment they travel through, and any obstacles in their path. Higher frequency microwaves have shorter ranges compared to lower frequency microwaves. However, it's important to note that microwaves, being a form of electromagnetic radiation, will continue to propagate until they are absorbed or scattered to the point of becoming undetectable.