1. Interference and Diffraction http://en.wikipedia.org/wiki/Diffraction

2. Huygens-Fresnel Principle Adapted from: Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. What if we block some of the wavelets?

3. Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. Diffraction increases as aperture size  Diffraction increases as aperture size  If is large compared to the aperture, the waves will spread out at large angles into the region beyond the obstruction. Diffraction

4. Diffraction Pattern From a Single Slit Ingle and Crouch, Spectrochemical Analysis

5. Diffraction Pattern From a Single Slit Ingle and Crouch, Spectrochemical Analysis For Destructive Interference: x = /2 W sin  = W sin  =

6. Diffraction Pattern From a Single Slit Ingle and Crouch, Spectrochemical Analysis For Destructive Interference: x = /2 W sin  = 2 W sin  = 2

7. Diffraction Pattern From a Single Slit Ingle and Crouch, Spectrochemical Analysis For Destructive Interference: W sin  = m W sin  = m m = ±1, ±2, ±3, …

8. Ingle and Crouch, Spectrochemical Analysis Eugene Hecht, Optics, Addison-Wesley, Reading, MA, 1998. W sin  = W sin  = sin   / W More accurately: sin  = 1.22 / W Diffraction Limited Beam Width

9. Airy pattern radius from central peak to 1 st minimum: Diffraction-limited resolution: http://www.microscopyu.com/articles/formulas/formulasresolution.html Diffraction-Limited Resolution

10. Eugene Hecht, Optics, 1998. Diffraction Gratings Plane or convex plate ruled with closely spaced grooves (300- 2400 grooves/mm). http://www.olympusmicro.com/primer/java/imageformation/gratingdiffraction/index.html

11. Two parallel monochromatic rays strike adjacent grooves and are diffracted at the same angle (  ). Difference in optical pathlength is AC + AD. For constructive interference: m = (AC + AD) m = 0,  1,  2,  3, … Ingle and Crouch, Spectrochemical Analysis Grating Equation

12. m = (AC + AD) AC = d sin  AD = d sin  Combine to give Grating Equation: d(sin  + sin  ) = m d(sin  + sin  ) = m Ingle and Crouch, Spectrochemical Analysis Grating Equation Grating Equation only applies if: d > /2

13. Are you getting the concept? At what angle would you collect the 1 st order diffracted light with = 500 nm if a broad spectrum beam is incident on a 600 = 500 nm if a broad spectrum beam is incident on a 600 groove/mm grating at  i = 10 ° ? For = 225 nm? For = 750 nm?