Single-Slit Diffraction and the Limit of Resolution
One slit spreads light into a wide central maximum with weaker ones either side, and the narrower the slit the wider that spread. The same spreading fixes the smallest detail a telescope or an eye can separate.
What a learner can do afterwards
- Describes how the pattern changes as the slit width or the wavelength changes
- Contrasts the uneven single-slit pattern with the even fringes from two slits
- Explains why a larger aperture separates finer detail
1 · Read
One narrow slit does not paint a sharp stripe. Light spreads into a broad bright centre with fainter fringes that fade fast either side. Make the slit narrower and that central band grows wider. The parts of the wavefront mix after the gap to make this shape.
Longer wavelengths spread more, so red paints a broader pattern than violet through the same gap. Short blue light stays tighter. This is why colour order matters whenever you read a pattern.
Two slits tell a different story: a comb of evenly spaced fringes of similar height. That regularity shouts two sources. No lens beats its own blur either: when one centre lands on its neighbour, detail merges. Bigger apertures narrow each blur, so wide mirrors split finer stars.
Narrow gaps spread light wide, colour sets the width, and wide apertures rescue fine detail.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.