![]() As viewed on the sheet of paper below the tank, the crests are the dark lines stretching across the paper and the troughs are the bright lines. These straight waves have alternating crests and troughs. If a linear object attached to an oscillator bobs back and forth within the water, it becomes a source of straight waves. Ripple tank demonstrations are commonly done in a Physics class in order to discuss the principles underlying the reflection, refraction, and diffraction of waves. As the waves encounter obstacles in their path, their behavior can be observed by watching the movement of the dark and bright spots on the sheet of paper. ![]() As the water waves move through the ripple tank, the dark and bright spots move as well. So the bright spots represent wave troughs and the dark spots represent wave crests. A crest of water will absorb more light than a trough. A portion of light is absorbed by the water as it passes through the tank. A light typically shines upon the water from above and illuminates a white sheet of paper placed directly below the tank. A ripple tank is a large glass-bottomed tank of water that is used to study the behavior of water waves. The study of waves in two dimensions is often done using a ripple tank. ![]() But what if the wave is traveling in a two-dimensional medium such as a water wave traveling through ocean water? Or what if the wave is traveling in a three-dimensional medium such as a sound wave or a light wave traveling through air? What types of behaviors can be expected of such two- and three-dimensional waves? Specifically, there will be some reflection off the boundary and some transmission into the new medium. Rather, a wave will undergo certain behaviors when it encounters the end of the medium. The wave doesn't just stop when it reaches the end of the medium. Demonstrations should be performed by qualified individuals only.Previously in Lesson 3, the behavior of waves traveling along a rope from a more dense medium to a less dense medium (and vice versa) was discussed. Demonstrations may pose a significant hazard and can, in some instances, result in death reasonable safety precautions must be taken. Warnings and precautionary measures listed on this site assume normal operation of equipment and are not inclusive. The author(s) assume no responsibility or liability for the use of information contained on this site. Reflection of waves from concave barriers Refraction of waves Barrier penetration by waves Bragg reflection of waves Superposition of pulses Effect of phase difference between sources Single slit diffraction Multiple slit diffraction Diffraction and scattering around obstacles Doppler effect wave velocity 19 cm/sec, two passes of dipper with source velocity 7 cm/sec, and two with source velocity 14 cm/sec Formation of shock waves Interference of wavesĭisclaimer: All demonstrations are posted for the convenience and benefit of faculty and staff in the Department of Physics at Simon Fraser University and are not intended for outside use. Water depths are 0.8 inches and 0.08 inches. With a further slight increase in the angle of incidence there is total reflection at the boundary.". The angle of incidence is increased until at a critical angle the refracted wave (in the deep water) runs just parallel to the boundary. As the wave crosses the boundary from shallow to deep water the wave velocity increases the wavelength is longer. Although most of the incident wave is refracted, part of it is reflected. ![]() When the periodic wave is incident at an angle on the boundary of the shallow region the wave fronts also bend, thereby changing the direction of propagation. Circular wave reflection from various barriers, 80-234, approx 2 minutes and 45 seconds From the notes: "The film first shows that the wave velocity decreases as the wave crosses a boundary from deep to shallow water. Angles are measured between the wave front and the barrier.Ī continuous periodic wave is reflected from the barrier placed at 45 degrees to the wave front. At 35 and 45 degrees the action is stopped and the angles of incidence and reflection are shown. (14 loops) Straight wave reflection from straight barriers, 80-231, approx 3 minutes Single straight pulses are reflected from a straight barrier placed parallel to the wave front, then at 35, 45 and 55 degrees.
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