Equipment: The equipment includes...
- basin of sand.
- bucket of water.
- ruler.
- cork.
Method: Land sand in a basin so that it is higher at one end. Fill the basin gently with water until half of the sand is covered under water. Using a ruler, make waves towards the beach from the "sea" water end of the basin. Note the effect of waves on the "beach". Place a cork on the water. Does it move towards the beach or up and down on the spot?
Now blow onto the surface of the water and note the effect of wind on sea currents.
Background knowledge: Water waves change as they approach the beach. The floating cork follows the water wave which is a transverse wave. This type of wave makes particles (eg. floating objects like a cork) move at right angles to the direction of the wave (ie. towards the beach). The other type of wave is a longitudinal wave where particles move in and out along the direction of the wave. A sound wave does this. The vocal chords vibrate and collide with air particles near by. The faster moving air particles then collide with other neighbouring air particles. In turn they collide again with other air particles. This wave that is set up travels through air to your ear and the close fast moving air particles then collide in the same way with your ear drum. The rate and pattern of these collisions match the vibration pattern from your vocal chords. Therefore, what you voice is saying is heard in the same pattern by your ear (ie. you hear the words your voice is communicating).