1. The Electromagnetic Spectrum

2. Optics and Photonics is an enabling technology and science It enables advances in many different disciplines of science, engineering, etc.

3. Radio Waves Power Transmission Radio Broadcasts

4. http://www.ovsa.njit.edu/ Radio Astronomy

5. Microwaves

6. Microwave source (Magnetron) melted a candy bar in Spencer’s pocket. The next day, he put an egg near the microwave source. It cooked and exploded….. The rest is history

7. Microwaves

8. Microwaves – Big Bang Discovery Cosmic background Radiation – Residual ‘Big Bang’ radiation from thermal ‘black body’ spectrum corresponding to radiation at T=2.7K

9. Terahertz (THz) Non-destructive Evaluation Security Screening

10. Picometrix NDE of Space Shuttle SOFI (Sprayed On Foam Insulation) –Insulates external tank –2 to 10 inches thick –Can break off during launch Non-destructive evaluation (NDE) desired to validate tank New NDE technique required: –<2 mm lateral resolution –Sensitive to voids and disbonds

11. High Resolution Imaging: 5x 400 x 400 mm

12. T-Ray Image of “Natural Voids” Space between stringers clear of voids or defects

13. Concealed Threats in Packaging Plastic knife and metal razor blade identified through packaging TRANSMISSION

14. Concealed Threats in Clothing Knife in shirt pocketExplosive simulant REFLECTION Unmodified

15. Infrared – Thermal Imaging

17. http://speclab.cr.usgs.gov Vegetation Mapping

19. Visible - Oximeter

21. UV-Sun/ Crab Nebula – Skin Cancer

22. X-rays

23. X-ray

25. Other things appear blue due to scattering…..

26. Three general classes of Scattering Depending on Particle size

27. Interference (Brief) Waves which are IN PHASE will add together. Waves which are OUT of phase, when added together will cancel each other

28. Consider a column of MANY scattering Centers…. In forward direction, scattered light forms a wavefront in the same direction (Secondary Wave) Primary wave

29. Even if scattering centers NOT in an organized row, forward going scattered light forms a new wavefront which transmits through medium

30. What about lateral (side) scattering? For a particular spacing between scattering centers, the scattered waves will DESTRUCTIVELY interfere and cancel each other Destructive interference Since there are MANY scattering centers (eg. number of atoms in a solid), we can ALWAYS add the scattering centers in pairs which individually destructively interfere.

33. Reflection from a boundary

38. Specular Reflection (from flat surface) Diffusion Reflection (from rough surface) Stealth fighter designed to avoid Diffuse Reflection from radar waves. Reflected waves directed so that reflected light does not retrace path back to be detected.

39. Huygen’s Principle Break up wavefront into individual points which each acting as a point source. Allow each spherical wavefront to propagate according to the local speed of light in the medium. Combination of spheres defines new wavefront. New wavefront is the line or curve of the crests/ troughs of the point sources of waves Direction of travel (ray) is perpendicular to wavefront

40. Refraction Pencil appears to be Bent at surface of water Object is DEEPER in water than it appears.

41. Light refracts because speed of light and radius of Huygen’s circle is different in the two mediums

42. http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=16 Generally, as light interacts at an interface between two medium, there is a reflected wave a refracted wave Animation of reflection/ refraction of light at a boundary

43. Example of Fermat’s Principle - Mirages Hot Air less dense so air travels FASTER Cold Air more dense so air travels SLOWER