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PRACTICE / Diffraction gratings

Covering the grating changes sharpness

An ideal uniformly illuminated grating resolves wavelengths near 600 nm in second order using 2400 slits. A mask then leaves only 1200 consecutive slits illuminated. Slit spacing is unchanged.

What is the new Rayleigh estimate of the minimum resolvable wavelength separation?

Organize the givens & assumptions
  • λ = 600 nm
  • m = 2
  • Remaining illuminated slits N = 1200

Ideal narrow-slit grating, normal incidence, small wavelength separation, uniform coherent illumination; order is accessible and not suppressed.

  1. A0.125 nm0.125\ \mathrm{nm}
  2. B0.500 nm0.500\ \mathrm{nm}
  3. C0.0625 nm0.0625\ \mathrm{nm}
  4. D0.250 nm0.250\ \mathrm{nm}

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