When tuning fork vibrates over on open pipe in the air in the pipe starts to vibrate the vibrations in the tube are caused by?

When a tuning fork vibrates over an open pipe, it produces sound waves that travel through the air and enter the pipe. These sound waves create pressure fluctuations that cause the air inside the pipe to vibrate as well. The vibrations in the tube are primarily caused by resonance, where the natural frequencies of the air column inside the pipe match the frequency of the tuning fork, amplifying the sound. This phenomenon leads to the formation of standing waves within the pipe, resulting in the characteristic sound of the vibrating air column.