Shown below is the central part of the interference pattern for a pure wavelength of red light projected onto a double slit. The pattern is actually a combination of singleand double-slit interference. Note that the bright spots are evenly spaced. Is this a double-or single-slit characteristic? Note that some of the bright spots are dim on either side of the center. Is this a single-or double-slit characteristic? Which is smaller, the slit width or the separation between slits? Explain your responses

The evenly spaced bright spots are a result of double-slit interference, where path differences between the two slits result in constructive interference, producing the bright spots.

The dimmer spots on either side of the center are a result of single-slit interference, where light from different parts of the same slit interferes with each other. The central bright spot is the most intense, and the intensity decreases as we move away from the center.

The fringe width of a single-slit interference pattern depends on the slit width: a smaller slit width results in a broader fringe pattern. In this case, the fringe pattern is composed of bright and dimmer spots (combination of single- and double-slit interference). The fact that there are dim spots on either side of the central bright spot indicates that the slit width must be smaller than the separation between the slits, as that would cause the broader, diffuse pattern corresponding to single-slit interference to overlap with the distinct bright spots formed due to double-slit interference. So, in conclusion: 1. The evenly spaced bright spots are a double-slit interference characteristic. 2. The dimmer spots on either side of the center are a single-slit interference characteristic. 3. The slit width is smaller than the separation between slits.