1. Refraction Physics Department, New York City College of Technology

2. Index of refraction Law of refraction Critical angle Total internal reflection Thin lens Thin lens equation Ray tracing Key words

3. Index of refraction • Definition • c is the speed of light in free space • v is the speed of light in a given material • n is unitless

4. Snell’s law 1 is the angle of incidence 2 is the angle of refraction Law of refraction (Snell’s law)

5. Example #1 • refraction

6. Total internal reflection • Occurs when light passes from high index material to a low index material • Critical angle C • For incident angles > C , there is no refracted ray => total internal reflection

7. Total internal reflection • Disc 22, #11

8. Optical path in fibers • Disc 22, #14

9. Example #2 • Total internal reflection

10. Converging lens Diverging lens Thin lenses

11. 3 special rays P ray F ray M ray Ray tracing

12. Ray tracing with lenses • Disc 22, #18

13. Magnification Thin lens equation

14. Sign conventions • f: + for converging lens,  for diverging lens. • do: + if on the side of the lens from which the light is coming; otherwise,  • di: + for a real image,  for a virtual image • hi: + for upright image,  for inverted image

15. Example #3 • Thin lens