15.2. Single Slit Interference http://www.ck12.org
15.2 Single Slit Interference
- Explain how single slit diffraction patterns occur.
- Use single slit diffraction patterns to calculate wavelength.
Though it looks like a double slit interference pattern, the pattern on the screen are actually the results of light
diffracting through a single slit with the ensuing interference.
Single Slit Interference
Interference patterns are produced not only by double slits but also by single slits, otherwise known assingle slit
interference. In the case of a single slit, the particles of medium at both corners of the slit act as point sources,
producing circular waves from both edges. These circular waves move across to the back wall and interfere in the
same way that interference patterns were produced by double slits.
In the sketch at below, the black lines intersect at the center of the pattern on the back wall. This center point is
equidistant from both edges of the slit. Therefore, the waves striking at this position will bein phase;that is, the
waves will produce constructive interference. Also shown in the sketch, just above the central bright spot where the
red lines intersect, is a position where destructive interference occurs. One of these red lines is one-half wavelength
longer than the other, causing the two waves to hit the wallout of phaseand undergo destructive interference. A
dark bank appears at this position.