Single Slit Diffraction Minima Condition — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Single Slit Diffraction Minima Condition Applies to Fraunhofer diffraction at a single slit where the screen is far from the slit (or focused by a lens). Assume a plane wavefront arrives at a slit of width 'a'. Divide the slit into two equal halves (zones) for the first minimum. The path difference between a wavelet from the top edge and one from the center is (a/2)sin(θ). For destructive interference, this path difference must be λ/2. Thus, (a/2)sin(θ) = λ/2 implies a sin(θ) = λ (for n=1). Generalize by dividing the slit into 2n zones to get a sin(θ) = n λ. The slit width 'a' must be comparable to the wavelength 'λ' for noticeable diffraction. Valid for minima only; n=0 corresponds to the central maximum, not a minimum. Assumes light is monochromatic and coherent. Confusing the single slit minima condition (a sinθ = nλ) with the double slit maxima condition (d sinθ = nλ). Thinking n=0 is a minimum; n=0 is actually the location of the central bright maximum. Applying the formula for maxima positions; maxima are approximately at (n + 0.5)λ.