10.3 WAVE MOTION
Waves play an important role in our daily life. It is because waves are carrier of energy and information over large distances. Waves require some oscillating or vibrating source. Here we demonstrate the production and propagation of different waves with the help of vibratory motion of objects.
Activity 10.1: Dip one end of a pencil into a tub of water, and move it up and down vertically (Fig. 10.6). The disturbance in the form of ripples produces water waves, which move away from the source. When the wave reaches a small piece of cork floating near the disturbance, it moves up and down about its original position while the wave will travel outwards. The net displacement of the cork is zero. The cork repeats its vibratory motion about its mean position.
Activity 10.2: Take a rope and mark a point P on it. Tie one end of the rope with a support and stretch the rope by holding its other end in your hand (Fig. 10.7). Now, flipping the rope up and down regularly will set up a wave in the rope which will travel towards the fixed end. The point P on the rope will start vibrating up and down as the wave passes across it. The motion of point P will be perpendicular to the direction of the motion of wave.