The higher the frequency, the more easily radio waves are absorbed or reflected by things like ordinary building materials and vegetation. Visible light, though far higher up the electromagnetic spectrum, demonstrates the principle nicely. A sheet of typing paper will let some light through, but a ½ inch piece of plywood will block it entirely. Radio waves behave in a similar fashion. They have much better penetration than visible light, but you wouldn’t bother trying to pick up the Cubs game if you were working in a bank vault.
Because higher frequencies are more easily reflected, they produce more multipath propagation, a phenomenon that occurs when transmitted signals bounce off an intervening object – even ordinary raindrops. The reflections cause different parts of the signal to arrive at the receiver at different times, and out of sequence. The worse the multipath propagation becomes, the more the signal begins to merge with the noise floor. " (automation.com) The issues with WiFi come down to the physics of radio waves. As the distance is added to the waves the faster they oscillate the more prone they are to what is called path loss.
