The Standing Wave Apparatus, for the demonstration of standing electromagnetic waves, (Seibt Effect) consists of a long glass tube on which is an evenly spaced winding of fine copper wire, a Bakelite mounting for supporting one end of the tube in the loop of the Cat. No. 50435 Short Wave Apparatus, and a support clamp for holding the other end of the tube.
Setting UP: Place the Cat. -No. 30435 Oscillator on a long table and connect it up as for ordinary operation. Its antenna arms should not be attached for this experiment. Fasten the Bakelite support to the top of the single turn inductor of the Cat. No. 30435 by means of the set-screw. Slip the bare end of the long tube through the hole in the Bakelite support and secure the rubber-covered end in the clamp support provided for that purpose.
Operation: When the short wave apparatus is set in operation, high frequency currents in the order of 75 x 10^6 cycles per second are induced in the long coil on the glass tube. These electromagnetic waves are reflected back from the open end of the coil and interfere with the oncoming waves to produce sharply defined voltage nodes and antinodes along the entire length of the winding. These nodes and antinodes may be beautifully demonstrated by holding the "Neon Wand" (Cat. No. 30457) at right angles to and with one end near to or touching the standing wave boil. As this neon tube is slowly moved along the coil, the discharge glow In the tube will slowly creep up the tube towards the band as a voltage antinode is approached, and will recede down the tube and finally disappear as a voltage node is reached. Eight or ten nodes and antinodes may be counted in this manner.
The electromagnetic field about the standing wave tube is so strong that the Neon Wand will often glow when two or three inches from the winding. Also, small incandescent lamps such as automobile headlight lamps or flashlight bulbs will often produce a bluish glow when the bulb of the lamp is brought against the winding on the tube. A Neon lamp such as our Cat. No. 54485, or a Neon spectrum tube such as our Cat. No. 37220 will glow similarly to the Neon Wand when brought near the Standing Wave Tube.
Another striking demonstration of the standing waves may be made by holding in the hand the bulb of a low wattage incandescent lamp such as our Cat. No. 79897 (110 volt 10 watt lamp) and with the brass base of the lamp touching the wire, slowly move the lamp along the coil. The 110 volt lamp will light up brightly as it passes a voltage antinode.
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