How does single-slit diffraction differ from double-slit interference?

Single-slit diffraction results in a central bright fringe surrounded by alternating dark and bright fringes, while double-slit interference produces evenly spaced bright fringes. For more detailed exploration, see diffraction patterns.

In single-slit diffraction, light waves passing through a narrow slit spread out and interfere with each other, creating a pattern of bright and dark fringes on a screen. The central fringe is the brightest and widest, with the intensity of the light decreasing for fringes further from the centre. This pattern is due to the constructive and destructive interference of the light waves. Constructive interference occurs when the waves are in phase, leading to a bright fringe, while destructive interference occurs when the waves are out of phase, resulting in a dark fringe. The width of the fringes in single-slit diffraction depends on the width of the slit and the wavelength of the light. Understanding wave parameters can further elucidate how these fringes form.

On the other hand, double-slit interference involves light passing through two closely spaced slits. The light waves from each slit spread out and overlap, creating an interference pattern of evenly spaced bright fringes on a screen. This pattern is also due to constructive and destructive interference. However, in double-slit interference, the bright fringes are equally bright and equally spaced, unlike in single-slit diffraction. The spacing of the fringes in double-slit interference depends on the distance between the slits and the wavelength of the light. For an in-depth understanding, consult the page on interference in double slits.

IB Physics Tutor Summary: In summary, single-slit diffraction causes light to spread out and form a pattern with a very bright centre and less bright fringes as you move away, due to light waves interfering with each other. Double-slit interference produces a pattern of bright fringes that are equally bright and spaced, resulting from light waves overlapping from two slits. The patterns differ in brightness, spacing, and how they're created.