Physics

Single-slit diffraction is fundamentally about how light bends around an obstacle—the width of the slit determines how much spreading occurs. The key insight is that the first dark fringe appears where light from opposite edges of the slit interferes destructively, and this happens at a specific angle determined by the wavelength. Use the single-slit dark fringe condition $a\sin\theta = m\lambda$ (where $m=1$ for the first dark fringe) along with the small-angle approximation to relate the fringe position on the screen to the slit width.

Single-slit diffraction is fundamentally about how light bends around an obstacle—the width of the slit determines how much spreading occurs. The key insight is that the first dark fringe appears where light from opposite edges of the slit interferes destructively, and this happens at a specific angle determined by the wavelength. Use the single-slit dark fringe condition $a\sin\theta = m\lambda$ (where $m=1$ for the first dark fringe) along with the small-angle approximation to relate the fringe position on the screen to the slit width.