A double-slit plate has two slits

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

A double-slit plate has two slits, each of width

b = 0.080\ \text{mm}

, with their centres separated by

d = 0.40\ \text{mm}

. The plate is illuminated by a plane wave and viewed in the far field (Fraunhofer regime), so the irradiance is

I(\theta) = 4I_0\left(\dfrac{\sin\beta}{\beta}\right)^2\cos^2\left(\dfrac{\pi d\sin\theta}{\lambda}\right)

, with

\beta = \pi b \sin\theta/\lambda

. ((a)) Which interference orders

m

(where

d\sin\theta = m\lambda

) are missing from the pattern? ((b)) How many bright fringes appear inside the central single-slit envelope (between its first zeros on either side)?

Related theory

Interference and diffraction

Browse the problem library