Waves on water

HOW

1. Create waves on water in several ways and observe them.
2. Press cyclically on the knob connected to the horizontal bar. In addition, by using a barrier system in the form of moving plates, you can observe the distortion of the waves passing through the gaps.
3. Press the knob on the other side of the station cyclically. It is connected to two small rollers. You can turn one of the rollers upwards – thus choosing whether you want the waves to be created by two rollers or by one of them.
4. Fill the container in the centre of the stand with water and watch the drops fall.
5. Note how the waves appear to be created at different vibration frequencies of the elements that form them.

WHY

The movement of steel elements or falling drops induces vibrations in the water molecules.

According to Huygens–Fresnel, a Dutch mathematician who lived in the 17th century, every point in the medium (here water) that a wave reaches itself becomes the source of a new spherical wave. This is easy to see just in the case of waves caused by falling drops or the impact of rollers against the water surface. For larger wave-inducing objects, the principle is the same, but more space is needed to observe that the propagating waves are spherical.

Close to the object, as in the case of our beam, the resulting wave is related to the shape of the inducing element. That is why you observe a plane wave.

The first of the propagating disturbances on the surface of water is called the wavefront, while the distance between two consecutive wave elevations is the wave length. The higher the frequency of vibration of the wave-forming element, the smaller the wave length. When two or more waves overlap, a phenomenon known as wave interference occurs. It manifests itself in vibrational amplifications and suppressions.