In a Young's double-slit experiment

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Interference and diffraction · Interference and diffraction

Optics and Photonics, Ch Fraunhofer diffraction from apertures and gratings

Problem

In a Young's double-slit experiment, two slits each of width b=0.20 mmb = 0.20\ \mathrm{mm} are cut with their centres separated by d=0.80 mmd = 0.80\ \mathrm{mm}. They are illuminated by light of wavelength λ=500 nm\lambda = 500\ \mathrm{nm} and the pattern is observed on a screen L=1.50 mL = 1.50\ \mathrm{m} away. ((a)) Using the point-source (idealised) treatment of Young's slits, find the spacing between neighbouring bright fringes on the screen. ((b)) The slits are not points but have finite width, so the fringes sit inside a single-slit diffraction envelope. Find which interference orders mm are missing, and state how many bright fringes are actually seen inside the central envelope. ((c)) Give the distance from the centre of the screen at which the first missing order would have appeared.

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