1. Fraunhofer Diffraction Geometrical Optics: …light can’t turn a corner. I Bill Mageors

2. Physical Optics: …actually, it can. I Francesco Maria Grimaldi Fraunhofer Diffraction

3. Huygens-Fresnel Principle Every point on a wavefront may be regarded as a secondary source of spherical wavelets. The propagated wave follows the periphery of the wavelets. Huygens, just add the wavelets considering interference! Augustin-Jean Fresnel (That’s a sweet ascot by the way.)

4. Far-Field Diffraction (a.k.a. Fraunhofer Diffraction) Far enough that source illumination is a plane wave. Far enough that diffracted wavelets are plane wave.

5. b ds s s sin  r Single Slit Fraunhofer Diffraction P

6. Get the amplitudes right! field amplitude field spherical wavelets: As ds goes to zero, dE o must go to zero: field amplitude per unit width

7. Get the phases right! (just like Young’s Double Slit) Integrate over the slit:

8. new variable: Calculate irradiance:

9. field at r an irradiance “sinc” “sampling function” “sine cardinal” Minima at: Maxima at: (graph it!)

10. Beam spreading