What's the difference between Young's interference and single-slit diffraction?

Young's interference involves two slits causing a pattern of bright and dark fringes, while single-slit diffraction involves one slit causing a central bright fringe surrounded by weaker fringes.

Young's interference, also known as double-slit interference, is a phenomenon that occurs when light waves pass through two closely spaced slits. This experiment was first performed by Thomas Young in the early 19th century, hence the name. As the light waves pass through the slits, they spread out and overlap, creating an interference pattern of alternating bright and dark fringes on a screen. The bright fringes, or maxima, occur where the waves constructively interfere, adding together to form a wave of greater amplitude. The dark fringes, or minima, occur where the waves destructively interfere, cancelling each other out. The pattern is symmetrical about a central maximum. For an in-depth exploration of interference patterns, consider reading about interference in double slits.

On the other hand, single-slit diffraction involves light passing through a single slit. This results in a diffraction pattern that consists of a central bright fringe, or maximum, surrounded by a series of weaker fringes on either side. The central maximum is much brighter and wider than the other fringes. This is because the light waves spread out, or diffract, as they pass through the slit, and interfere with each other on the other side. The central maximum occurs where the waves interfere constructively, while the weaker fringes occur where the waves interfere destructively. The pattern is not symmetrical, with the intensity of the fringes decreasing as you move away from the central maximum. The phenomena of diffraction and the resulting patterns are further elaborated on in the discussion of diffraction patterns.

IB Physics Tutor Summary: In simple terms, Young's interference (double-slit) creates a pattern with alternating bright and dark lines from light passing through two slits, due to waves adding up or cancelling out. Single-slit diffraction produces a bright central line with dimmer lines on each side from light through one slit, spreading and overlapping. The first is about light waves mixing from two sources; the second, from just one. To understand how these patterns form from a physics perspective, you may want to look into wavefronts and rays, which explains the concepts behind the propagation of light waves.