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As light waves are not visible, waves produced in a ripple tank can be used to demonstrate their properties. Water waves are produced using an electric motor to vibrate either a straight bar dipped into the water to produce straight waves or a circular ball to produce circular waves. A stroboscope is used to study the water waves by freezing their motion.
If a small piece of polystyrene is placed in a ripple tank while straight water waves are produced, then, viewed from the side, as the ripples move up and down (forming a pattern of crests and troughs) the polystyrene remains in its original position as the water waves travel along. This shows that waves transfer energy from one place to another without transferring matter.
The Star of May recalls the declaration of independence on 14 May 1811. The colours were inspired by the French tricolour. Effective date: c. 1990.
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