An electromagnetic wave follows the laws of motion and propagation described by Maxwell's equations, which are a set of fundamental equations in electromagnetism. These equations govern the behavior of electric and magnetic fields and their interplay with each other.
When an electromagnetic wave is launched from a source, such as a magnetron, its propagation depends on several factors:
Straight-line Propagation: In the absence of any external influences or interactions, an electromagnetic wave will propagate in a straight line. This is known as rectilinear propagation. The wave will continue to propagate with a constant velocity, which is the speed of light in a vacuum (approximately 299,792 kilometers per second or 186,282 miles per second).
Reflection: When an electromagnetic wave encounters a reflective surface, such as a mirror or a metallic object, it can undergo reflection. The angle of incidence (the angle at which the wave strikes the surface) will be equal to the angle of reflection (the angle at which the wave is reflected). This phenomenon allows waves to change direction but does not dissipate the wave.
Refraction: If an electromagnetic wave passes from one medium to another with a different refractive index (a measure of how much the wave's speed changes in that medium), it can undergo refraction. This results in a change in direction and possibly a change in wavelength. Refraction occurs at the boundary between the two media and does not dissipate the wave.
Absorption and Attenuation: Electromagnetic waves can be absorbed or attenuated by certain materials or substances. When a wave interacts with a medium that absorbs its energy, such as a solid object or a dense gas, the wave's intensity can decrease as it propagates through the medium. The extent of absorption and attenuation depends on the properties of the material and the wavelength of the wave.
Regarding how far an electromagnetic wave can propagate, theoretically, it can travel indefinitely in the absence of any significant obstacles or interactions that would cause its energy to dissipate or be absorbed. In the vacuum of space, an electromagnetic wave can propagate over vast distances without a substantial loss of energy. However, as mentioned earlier, interactions with the interstellar medium, gravitational lensing, or cosmic background radiation can affect the propagation of the wave to some extent.