What are the main problems of signal propagation why do radio waves not always follow a straight why is reflection both useful and harmful?

The main problems of signal propagation include absorption, scattering, and reflection which can cause attenuation and signal degradation. Radio waves do not always follow a straight path due to factors like obstacles, atmospheric conditions, and interference, leading to signal loss and distortion. Reflection is useful in communication for extending coverage range through bouncing signals off surfaces, but it can also create multipath interference and echo effects, leading to signal distortion and quality degradation.