Reflection and Refraction: Understanding Light Rays and Lenses

1. Chapter 21 • Reflection and Refraction

2. The Ray Model of Light Light rays travel in straight lines. Light rays can cross. A light ray travels forever unless it interacts with matter. An object is a source of light rays. The eye sees by focusing a bundle of rays. Slide 18-9

3. Sources of Light Rays: Self-Luminous Objects A ray source A point source A parallel-ray source An extended source Slide 18-10

4. The Law of Reflection The incident ray and the reflected ray are both in the same plane, which is perpendicular to the surface, and The angle of reflection equals the angle of incidence: θr = θi . Slide 18-15

5. Refraction Slide 18-17

6. Snell’s Law of Refraction Slide 18-18

7. Example Problem What is the index of refraction of the plastic if a ray is refracted as in the figure? Slide 18-20

8. Total Internal Reflection Slide 18-21

9. Thin Lenses and Ray Tracing The focal point of a converging lens The focal point of a diverging lens Slide 18-23

10. Three Important Sets of Rays: Converging Lenses Slide 18-24

11. Ray Tracing: Real Images Slide 18-25

12. Checking Understanding Which of these ray diagrams is possibly correct? Slide 18-27

13. Answer Which of these ray diagrams is possibly correct? D Slide 18-28

14. Magnification of a Lens or Mirror Slide 18-29

15. Ray Tracing: Virtual Images Slide 18-30

16. Checking Understanding In this figure the image is produced by a lens. At which position A–E is the lens? Slide 18-33

17. Answer In this figure the image is produced by a lens. At which position A–E is the lens? D Slide 18-34

18. Three Important Sets of Rays: Diverging Lenses Slide 18-31

19. Three Sets of Special Rays for a Concave Mirror Slide 18-36

20. A Real Image Formed by a Concave Mirror Slide 18-37

21. Three Sets of Special Rays for a Convex Mirror Slide 18-39

22. Ray Tracing for a Convex Mirror Slide 18-40

23. The Thin-Lens Equation Slide 18-42

24. Summary Slide 18-44