Chapter 15 Review Light and Refraction

1. Chapter 15 Review Light and Refraction

2. 1. Define refraction.

3. Refraction is the term for the bending of a wave disturbance as it changes speed.

4. 2. How does light refract when the light ray slows down?

5. When light slows down it bends toward the normal.

6. 3. How does light refract when the light ray speeds up?

7. When light speeds up it bends away from the normal.

8. 4. A light ray passes from air into water (n = 1.33) at an angle of 42°. What is the angle of refraction?

9. n1 sinq1 = n2sinq21sin42° = 1.33sinq2q2 = 30°

10. 5. A light ray passes from water (n = 1.33) into diamond (n = 2.4) at an angle of 55°. What is the angle of refraction?

11. n1 sinq1 = n2sinq21.33sin55° = 2.4sinq2q2 = 27°

12. 6. A light ray passes from glass (n = 1.5) into air (n = 1) at an angle of 15°. What is the angle of refraction?

13. n1 sinq1 = n2sinq21.5sin15° = 1sinq2q2 = 23°

14. 7. A convex lens has a focal length of 12 cm. If an object is placed 18 cm from the lens, where is the image formed? What is the image’s type and orientation? What is the magnification? If the object is 2 cm tall, how big is the image? Draw a ray diagram of this situation.

15. 1/f = 1/do + 1/di1/12 = 1/18+ 1/didi = 36 cm real, inverted, larger M = di /do = 36/18 = -2 hi/ho = di /dohi/2 = 36 /18 hi = 4 cm

16. The object is located between one focal length and two focal lengths.

17. A line parallel to the axis is bent so it passes through the focal point on the opposite side.

18. A line that is directed through the focal point on the same side is refracted parallel. Where the rays cross is the image point.

19. A ray directed through the optical center of the lens will also cross at this point.

20. 8. A convex lens has a focal length of 20 cm. If an object is placed 10 cm from the lens, where is the image formed? What is the image’s type and orientation? What is the magnification? If the object is 2 cm tall, how big is the image? Draw a ray diagram of this situation.

21. 1/f = 1/do + 1/di1/20 = 1/10+ 1/didi = -20 cm virtual, upright, larger M = di /do = 20/10 = 2 hi/ho = di /dohi/2 = 20/10 hi = 4 cm

22. A ray from the top of the object that is parallel to the principal axis refracts through the focal point on the opposite side.

23. A ray through the optical center goes straight through. Since the two rays diverge, they must be extrapolated back to see where they cross.

24. This is a virtual, upright, larger image. A magnifying glass.

25. You could also draw a ray that appears to leave from the focal point on the same side. It refracts parallel and its extrapolation also crosses at the image.

26. 10. An object is placed 12 cm from a concave lens that has a focal length of -9 cm. What is the object’s distance from the lens? Draw a ray diagram of this situation.

27. 1/f = 1/do + 1/di1/-9 = 1/12+ 1/didi = -5.14 cm virtual, upright, smaller M = di /do = 5.14/12 = 0.43

28. Focal point at -9 cm, object at 12 cm.

29. A ray parallel to the principle axis is diverged so it appears to come from the near focal point.

30. A ray through the optical center of the lens is not bent. Where the two rays cross is the image.

31. A ray through the opposite focal point is refracted parallel and, if extended back, also crosses at the image.

32. 11. Describe the image formed by a convex lens when the object is placed between infinity and two focal lengths from the lens.

33. Real, inverted, smaller.

34. 12. Describe the image formed by a convex lens when the object is placed between two focal lengths and the focal point.

35. Real, inverted, larger.

36. 13. Describe the image formed by a convex lens when the object is placed between the focal point and the lens.

37. Virtual, upright, larger.

38. 14. Describe the image formed by a concave lens when the object is placed between infinity and two focal lengths from the lens. 15. Describe the image formed by a concave lens when the object is placed between two focal lengths and the focal point.16. Describe the image formed by a concave lens when the object is placed between the focal point and the lens.

39. Virtual, upright, smaller. (That is all that ever results with a concave lens.)

40. 17. What is total internal reflection?

41. When a light ray is speeding up and the angle of refraction reaches 90°, if the angle of incidence increases, the light ray is totally reflected at the boundary to the two media.

42. 18. Calculate the critical angle for a glass (n = 1.5) to air boundary.

43. n1 sinq1 = n2sinq21.5sinq1= 1sin90°1.5sinq1= 1q1 = 42°

44. 19. Calculate the critical angle for a diamond (n = 2.4) to air boundary.

45. n1 sinq1 = n2sinq22.4sinq1= 1sin90°2.4sinq1= 1q1 = 24.6°

46. 20. How are mirages formed?

47. Hot air by the ground causes the light to be refractedinto your eyes. You see this image in a different location and that is a mirage.

48. Hot air by the ground causes the light from the sky to be refracted into your eyes. You see an image of the sky on the ground and our experience tells us it is reflected in water.

49. 21. How does atmospheric refraction affect the time of sunrise and sunset?

50. The atmosphere refracts sunlight toward the surface of the earth. This allows the sun to be seen after it has passed below the horizon and before it moves above the horizon. This adds about 4 minutes to each day.