1. Reflection & Refraction of Electromagnetic Radiation By Emin Menachekanian, PhD

2. What Is Light? ɤ

3. Electromagnetic Spectrum

4. The Speed of Light Is Finite, But Fast! Consider the round-trip distance from here to UCLA and back: 30 mi ≈ 60 km

5. The Speed of Light Is Finite, But Fast! Voyager 1, launched in 1977, took about 30 years to reach the edge of our solar system. Light would take about 12 hours to do the same thing!!

6. Understanding How Light Reflects & Transmits Use: Fermat’s Principle of Least Time

7. Pierre de Fermat

8. Fermat’s Principle of Least Time Light will always take the path from one point to another that minimizes the time of its journey.

9. What About for Reflecting from a Mirror? Mirror

10. Mirror Image

11. What’s the Correct Reflection? Mirror A B Equidistant to Mirror B’ This path not only minimizes the distance, but it also minimizes the time! Because speed of incident ray is the same as the speed of reflected ray.

12. Law of Reflection Mirror A B Normal to Mirror θiθi θrθr θ i = θ r

13. Why Does He Look Like This?

14. Simple Example Mirror

15. Simple Example Mirror

16. Simple Example Mirror

17. Transmission of Light It takes time for the light to be re- emitted when captured → Slows down! Speed of light in medium Speed of light in empty space Index of Refraction

18. Indices of Refraction for Various Materials

19. Which One Is The Shortest Distance? A B C 50 m 85 m 25 m

20. Which One Takes The Least Time? A B C Running Speed Is 10 m/s Swimming Speed Is 2.5 m/s 5 s 20 s 8.5 s 10 s

21. Which One Takes The Least Time? A B C Fast Slow

22. Light Behaves the Same Way! As light enters from a medium with a LOW index of refraction to one with a HIGH index of refraction, the ray bends TOWARDS the normal. As light enters from a medium with a HIGH index of refraction to one with a LOW index of refraction, the ray bends AWAY FROM the normal.

23. Refraction Simulator http://interactagram.com/physics/optics/refraction/

24. The “Bent” Pencil

25. Water Actual Straw Image of Straw

26. Full Reflection from Medium Interface!

27. Total Internal Reflection Only occurs when light is going FROM a medium with a HIGHER index of refraction INTO a medium with a LOWER index of refraction http://interactagram.com/physics/optics/refraction/

28. The Critical Angle The angle (with respect to the normal) at which the light totally internally reflects is known as the critical angle. The larger the index of refraction of the medium in which the light totally internally reflects, the smaller the critical angle.

29. Critical Angles (Surrounding Medium: Air) Internal MediumRefractive Index (n)Critical Angle [Deg.] Water1.3348.8 Ethyl Alcohol1.3647.3 Quartz, Fused1.4643.2 Lucite1.5041.8 Glass, Crown1.5241.1 Glass, Flint1.6637.0 Zircon1.9231.4 Diamond2.4224.4

30. 45° Glass Prisms > 41° (TIR)

31. Binoculars

32. Fiber-Optic Cables