What is single-slit diffraction?

Single-slit diffraction is a phenomenon where light passing through a narrow slit spreads out, creating an interference pattern.

In more detail, single-slit diffraction is a fundamental concept in wave optics, which is the study of light as a wave phenomenon. It occurs when a wave encounters an obstacle or a slit that is comparable in size to its wavelength. The wave doesn't just continue in a straight line, but it bends around the corners of the obstacle or spreads out after passing through the slit. This bending or spreading out of the wave is known as diffraction.

The most common example of single-slit diffraction is when light passes through a narrow slit and forms a pattern of light and dark bands on a screen behind the slit. This pattern is called an interference pattern because it results from the interference of the light waves with each other. The central band, or central maximum, is the brightest because this is where the most constructive interference occurs. On either side of the central maximum are alternating dark and light bands, or minima and maxima, where destructive and constructive interference occur, respectively.

The pattern's width depends on the wavelength of the light and the width of the slit. If the slit is made narrower or the wavelength of the light is increased, the diffraction pattern becomes wider. This relationship is described by the equation θ = λ/b, where θ is the angle of the first minimum, λ is the wavelength of the light, and b is the width of the slit.

Single-slit diffraction is a crucial concept in understanding the wave nature of light. It demonstrates that light doesn't always travel in straight lines, but can bend around corners and spread out, behaving like a wave. This understanding is fundamental to many areas of physics and engineering, including the design of optical instruments like microscopes and telescopes.