1. 18 Ray Optics
Slide 18-2

2. Slide 18-3

3. Slide 18-4

4. Light rays travel in straight lines.
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

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

6. Seeing Objects Seeing a point or extended source
Seeing an object by scattered light
Seeing a ray source
Slide 18-11

7. Shadows
Slide 18-12

8. 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

9. The Plane Mirror
Slide 18-16

10. Refraction
Slide 18-17

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

12. Slide 18-19

13. Total Internal Reflection
Slide 18-21

14. Locating a Virtual Image
Slide 18-22

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

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

17. Ray Tracing: Real Images
Slide 18-25

18. Slide 18-26

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

20. Ray Tracing: Virtual Images
Slide 18-30

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

22. Slide 18-32

23. Spherical Mirrors and Ray Tracing
The focal point of a concave mirror
The focal point of a convex mirror
Slide 18-35

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

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

26. Slide 18-38

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

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

29. Slide 18-41

30. The Thin-Lens Equation
Slide 18-42

31. Slide 18-43

32. Summary
Slide 18-44

33. Reading Quiz
When an object like a tree is illuminated by the sun, and you are looking toward the tree, light rays leave the object
only from points at the top and base of the tree, but in every direction.
from every point on the surface of the tree, but only toward your eyes.
only from points at the top and base of the tree, but only toward your eyes
from every point on the surface of the tree and in every direction.
Answer: D
Slide 18-5

34. Answer
When an object like a tree is illuminated by the sun, and you are looking toward the tree, light rays leave the object
only from points at the top and base of the tree, but in every direction.
from every point on the surface of the tree, but only toward your eyes.
only from points at the top and base of the tree, but only toward your eyes
from every point on the surface of the tree and in every direction.
Answer: D
Slide 18-6

35. Reading Quiz
A light ray can change direction when going from one material into another. This phenomenon is known as
reflection.
absorption.
refraction.
scattering.
Answer: C
Slide 18-7

36. Answer
A light ray can change direction when going from one material into another. This phenomenon is known as
reflection.
absorption.
refraction.
scattering.
Answer: C
Slide 18-8

37. Example Problem
If the aperture is very small, how far apart on the screen built into the left side of the box are the images of the point-like red and green light sources?
Slide 18-13

38. Example Problem
If the aperture is a circle 1 cm in diameter, what are the size and shape of the image of the green point-like light source? Do you need to know how far below the center of the aperture that source is?
Slide 18-14

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

40. Checking Understanding
Which of these ray diagrams is possibly correct?
Answer: D
Slide 18-27

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

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

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