Formation of Waves

Wave on a Rope

Onda Transversal en una cuerda

The animation above shows the creation of a simple wave that moves along a rope. The hand holding on to one end of the rope is flicked up and then down to create a single pulse in the rope. An upward displacement in the rope is created by the flick of the hand. This disturbance moves away from the hand, carrying energy along the rope. The pulse travels along the rope as each segment of the rope affects the next segment. This happens because the rope is under tension. When one segment of the rope is displaced, it pulls on the neighboring segments, causing them to move as well. As the pulse travels, each segment of the rope moves up and then back down to its original position, transferring the energy of the disturbance along the rope. The movement of the rope segments creates a traveling wave, which is a pulse in this case.

If the hand repeatedly goes up and down, a continuous waveform will be set up.

In the above animation, two key ideas about a wave is demonstrated:

  1. Energy transfer: The wave carries energy from the point of disturbance (the hand) to the other end of the rope.
  2. Matter is not transferred: The pulse (or whichever form the wave takes) moves in the direction of energy transfer but the medium through which the energy is carried, which in this case, is the rope segments, do not move from one end to another of the rope. Instead, each segment only oscillates about a fixed position.

Simply put, waves transfer energy without transferring matter.

Wave on a Ripple Tank

A ripple tank demonstrates wave motion by creating ripples on the water's surface when a vibrating source with a motor, such as a round end or a long paddle, disturbs the water. The light from above the ripple tank illuminates the water surface, casting shadows of the ripples onto the bottom of the tank or a projection screen. These shadows make the wave patterns more visible and allow for observation of their behavior and interaction, such as interference and diffraction.

The bright lines are formed through refraction of light, converging as rays of light pass through the crest. The particles in these waves are said to be in phase, or oscillating with the same displacement and velocity at the same time.