These lines of interference are caused by phase shifts from one source to the other dependent upon how far one wave has travelled with respect to the other wave, given they are in phase to begin. There is also a Thin Slit Diffraction demo available to demonstrate the discovery of this phenomenon. This pattern is easily demonstrated by our Interference Model. Two slit interference pattern showing destructive interference (dark lines) and constructive interference (bright lines). This interference pattern produced lines of constructive and destructive interference called antinodes and nodes, respectively. What he found is that the light wavelengths diffract through the slits and produce a pattern of interference (see Fig 1). The experiment was first performed by Thomas Young in 1801, where he displayed incident light being shone upon two small cuts in a boundary. This is a demonstration of the famous double-slit interference pattern, which was the forefront discovery of superposition in wavelengths. 2kHz works best for this while using a directional microphone as recommended. Students should see maxima and minima of the interference on the oscilloscope screen. Plug in the banana jacks from the microphone to the adaptor. To hook up the microphone use the BNC – banana input adaptor and connect it to Channel 1 of the oscilloscope. Optional: Instructor can use the oscilloscope and a microphone (shown in picture) and walk back and forth in front of the speakers with the microphone in hand. Now have the students plug one ear and move their heads around to hear the minima and maxima produced by sound interference. This seems to be the optimum frequency for use with the microphone, however, 500 – 2500Hz usually work for students. Plug in the speakers to the generator using banana cables and raise the frequency of the generator to approximately 2000 Hz. To demonstrate the interference, place the speakers 1m apart using the measuring stick and direct them towards the students. Tektronix TDS 2001C Oscilloscope (optional).Function Generator (Frendrikson Function Generator works best). It is able to produce a two slit interference pattern within the lecture hall, allowing students all around the lecture hall to hear the nodes and antinodes that occur due to superposition of sound waves. This apparatus demonstrates simple two-slit interference patterns in sound waves.
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