PHYS 123 Chapter Notes - Chapter 34: Diffraction Grating, Matter Wave, Radiography
Document Summary
Diffraction is indeed observed with light but only when width of opening is not much greater than wavelength of light. Distant point sources can be considered as sources of planar waves. Intensity of planar wave is uniform as the wave propagates forward because the fields from individual wavelets cancel in all directions and reinforce in the direction of propagation. The waves interfere destructively in any other than the direction of propagation of the wave fronts. This is only true when width of wave fronts is much greater than the wavelength of the light. When width is comparable to the wavelength of the light. As each wave front of the beam reaches the barrier, only the portion that hits the gap continues moving . The width of each wave front that passes through the gap is equal to the gap width. Some of the light spreads out past edges of the original path of beam, the light is diffracted.
