section_path: Principles/Limiting factors/Beam path and range
section_name: Beam path and range
paragraph_text: Beam path and range
  
  A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the refractive index of air, which is called the radar horizon. Even when the beam is emitted parallel to the ground, the beam rises above the ground as the curvature of the Earth sinks below the horizon. Furthermore, the signal is attenuated by the medium the beam crosses, and the beam disperses.
  
  The maximum range of conventional radar can be limited by a number of factors: