Interference

W.4(1) - Ripple Tank

A ripple tank produces straight waves, circular waves, and waves from two sources with variable phase adjustment. It can be used to illustrate Huygen's Principle of Wave Motion and other phenomena such as refraction, reflection, diffraction and interference. It consists of a 50 cm diameter glass tank standing on three 30 cm tall stands. The wave producing device is a motor-driven generator powered by a 6 volts DC power supply. The frequency of vibration is controlled by the speed of the motor which is a function of the applied voltage. A stand supports the generator at the tank's height. The tank is a set on a overhead projectorand the patterns projected on a screen for a better visibility. It is filled with a 1-2 cm layer of water. The accessories provided allow the production of waves due to a single point source, two point sources ( with phase adjustment) and a straight bar source, that can be easily exchanged. A strobe light can also be used to permit the wave action to be viewed at frequent intervals creating an illusion that the standing still or moving slowly.

 

 

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W.4(2) -Phase Difference Wave Machine

 

It allows to demonstrate the superposition of two sine waves of differing amplitudes and frequencies. It consists of a series of 41 vertical metal rods mounted in a wood frame. Sliding on each of the rods are two colored beads separated by a sleeve. The lower series of beads rests on the bottom of the frame and is green, with a black bead replacing every eighth one to mark phase. The upper bead series is red, and the lengths of the sleeves are adjusted so the red beads trace 2.5 wavelengths of a sine wave, with a bead every 22.5 degrees of phase.

Two separate plexiglass sine wave profiles slide into a slot in the bottom of the frame, raising the beads to form a combined wave. The larger profile has the same wave parameters as the basic unit, and demonstrates constructive and destructive interference. The smaller profile has a wave of twice the frequency and half the amplitude, to demonstrate overtones.

The apparatus measures 77 cm x 32 cm x 7 cm overall.

 

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