Fraunhofer Diffraction
Demonstration of Fraunhofer diffraction on various apertures in a screen: single slit, double slit, diffraction grating, circular aperture.
Experimental setup for diffraction study. He-Ne laser, polarizing filter, lens f = +5 mm, lens f = +50 mm, holder for diffraction slides.
Experimental setup.
Detail of expanded laser beam illuminating the slide.
Various diffraction slides:
46985 – double slits with constant width (b) and variable separation (g) (dimensions in mm)
46984 – double slits with constant separation (g) and variable width (b)
46996 – circular apertures with radii (from left) 0.12 mm, 0.24 mm, 0.48 mm
46997 – "inverse slits" with widths (from left) 0.2 mm, 0.4 mm, 0.8 mm
46991 – slits of varying width (from left) 0.12 mm, 0.24 mm, 0.48 mm
46987 – diffraction gratings with grating constants of 20, 40, and 80 lines per centimeter (corresponding to slit spacing (g) in mm)
46986 – diffraction gratings with 2, 3, 4, 5, and 40 slits, slit spacing (g) 0.25 mm, slit width (b) 0.2 mm.
Diffraction from single slits of various widths. The spacing of maxima/minima is inversely proportional to the slit width.
Diffraction from a single slit of width 0.12 mm.
Diffraction from a single slit of width 0.24 mm.
Diffraction from a single slit of width 0.48 mm.
Diffraction from inverse slits of various widths. According to Babinet’s principle, diffraction patterns from complementary screens are identical except for the central maximum. The spacing of maxima/minima is inversely proportional to slit width.
Diffraction from an "inverse slit" 0.2 mm wide.
Diffraction from an "inverse slit" 0.4 mm wide.
Diffraction from an "inverse slit" 0.8 mm wide.
Diffraction from double slits with various separations. The spacing of maxima/minima is inversely proportional to slit separation.
Diffraction from double slits, width 0.2 mm, separation 0.25 mm.
Diffraction from double slits, width 0.2 mm, separation 0.5 mm.
Diffraction from double slits, width 0.2 mm, separation 1 mm.
Diffraction from double slits of various slit widths. The interference pattern is modulated by an envelope determined by the finite slit width. Changing the slit width alters the modulation but not the spacing of maxima/minima.
Diffraction from double slits, width 0.1 mm, separation 0.25 mm.
Diffraction from double slits, width 0.15 mm, separation 0.25 mm.
Diffraction from double slits, width 0.20 mm, separation 0.25 mm.
Diffraction from varying number of slits. With more slits, the main maxima become narrower and additional weaker maxima appear between them, the number of which depends on the slit count.
Diffraction from 2 slits, width 0.2 mm, separation 0.2 mm.
Diffraction from 3 slits, width 0.2 mm, separation 0.2 mm.
Diffraction from 4 slits, width 0.2 mm, separation 0.2 mm.
Diffraction from 5 slits, width 0.2 mm, separation 0.2 mm.
Diffraction from 40 slits (not all illuminated), width 0.2 mm, separation 0.2 mm.
Diffraction from gratings with various grating constants. The grating constant defines the number of slits per unit length. The larger the constant, the smaller the slit spacing, and the more spread out the diffraction pattern becomes.
Diffraction from grating with 20 lines per cm.
Diffraction from grating with 40 lines per cm.
Diffraction from grating with 80 lines per cm.
Diffraction from circular apertures of different diameters. The diffraction pattern consists of concentric rings. Their spacing is inversely proportional to the aperture diameter.
Diffraction from a circular aperture of diameter 0.48 mm.
Diffraction from a circular aperture of diameter 0.24 mm.
Diffraction from a circular aperture of diameter 0.12 mm.
Diffraction from a square grid and its inverse. See also Diffraction pattern from complementary apertures.
Diffraction from a square grid.
Diffraction from an "inverse" square grid.