PURPOSE: To show the standing waves of a vibrating string. That is, to show the modes of vibration for a continous system.
DESCRIPTION: A long string is stretched across the room. The sequence of harmonics for the normal modes, from the high frequency cut off down to the fundamental limit, can be shown. The nodes, anti-nodes and the polarity of the waves can be seen.
Keep the tension in the rope fixed and change the frequency to show that wavelength is different, therefore the speed of the wave is constant. Keep the frequency fixed and change the tension to show that the wavelength is different, and the speed of the wave is changed.
A strobe can be used to slow down the motion of each mode. A string of blacklights can be used to help illuminate the string.
EQUIPMENT: Vibrating string system with function generator and vibrator, strobe, blacklights as photographed below.
Updated by Jun Qi in 3/24/2000