PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction
What an Instrument Can See, Ch Scalar diffraction theory, derived
Problem
Two closely spaced spectral lines near λ=580.0nm, separated by Δλ=0.0060nm, are to be resolved with a diffraction grating ruled at 500 lines per millimetre, used in second order (m=2).
((a)) Find the resolving power R required to just resolve the two lines by the Rayleigh criterion.
((b)) Find the minimum number of illuminated grooves N needed to reach this R in second order.
((c)) Find the minimum illuminated width of the grating this requires.
((d)) A ruled area 100mm wide is available. State whether the requirement of part (a) can be met using the full width in the same order, and give the resolving power actually achieved.