Q. A single rectangular aperture with a width of 0.30 mm and a height of 0.50 mm is illuminated at normal incidence by a uniform plane wave of laser light with a wavelength of 633 nm. The diffraction pattern produced by the aperture is observed on a screen at a distance of 4.0 m from the aperture. The power density at the centre of the diffraction pattern is measured to be 7.0 W/m2.
(a) Verify that the Fraunhofer condition is satisfied in this situation.
(b) What is (a) the width and (b) the height of the central bright maximum of the diffraction pattern, measured between the two dark fringes on either side?
(c) What is the power density half way between the first and second dark fringes on one side of the central maximum?