Geometric Optics: Law of Reflection Explained

1. Geometric Optics Review

2. In the law of reflection the angle of incidence • is always greater than the angle of reflection • is always less than the angle of reflection • depends on the index of reflection and the angle of reflection • is always equal to the angle of reflection

3. The reason that you see a streak of light from the surface of a lake is that • The index of refraction of the water is greater than that of air • Light bends into the water and then gets scattered out • The surface of the water is rough • The surface of the water is smooth

4. The name for reflection from a smooth surface is • planar • specular • internal • diffuse • normal

5. The kind of reflection that allows us to see objects is • planar • specular • internal • diffuse • normal

6. In the above diagram, the angle of incidence is 20º • 20º • 50º • 70º • 90º

7. In the above diagram, the angle of reflection will be 20º • 20º • 50º • 70º • 90º

8. The angle of reflection can never be greater than • 0º • 45º • 90º • 180º

9. The angle of incidence can never be greater than • 0º • 45º • 90º • 180º

10. An image seen in a plane mirror is always • upright and real • upright and virtual • inverted and real • inverted and virtual

11. The magnification of an object in a plane mirror is • <1 • negative • >1 • 1

12. For a plane mirror, if the object is 10m in front of the mirror, then the image is • At the mirror • Less than 10m in front of the mirror • 10m in front of the mirror • Less than 10m behind the mirror • 10m behind the mirror • More than 10m behind the mirror

13. For a spherical mirror with radius, r, the focal length, f is given by: • f=2r • f=r • 2f=r

14. 2 cm In the above diagram, the magnification is Image Object 3 cm • 0.5 • -0.5 • 1.0 • -1.0 • 1.5 • -1.5

15. 2 cm In the above diagram, the image is Image Object 3 cm • virtual • imaginary • real

16. 2 cm In the above diagram, the object distance is 4 cm Image Object 3 cm • 2 cm • 3 cm • -3 cm • 4 cm • 6 cm

17. 2 cm In the above diagram, the image distance is 4 cm Image Object 3 cm • 2 cm • 3 cm • -3 cm • 4 cm • 6 cm

18. For mirror lenses, when the image distance is positive the image is • virtual • real

19. For glass lenses, when the image distance is positive the image is • virtual • real

20. If an image is upright, it must be • real • virtual

21. Do the light rays from a virtual image cross at the image location? • Yes • No

22. OF COURSE! YOU ONLY SEE THINGS WHEN THE IMAGE IS FOCUSED ON YOUR RETINA. Can the light rays from a virtual image be focused on your retina? • Yes • No

23. For the object above, which is a possible real image C Object B A D • A • B • C • D

24. For the object above, which is a possible virtual image C Object B A D • A • B • C • D

25. You want an image that is both real and upright. You need to use • A mirror lens • A glass lens • Neither will work

26. A The object and focal points are shown. Which is not a principle ray? B C D • A • B • C • D

27. For a spherical mirror, light that travels through the center of the sphere reflects • Parallel to the main axis • Through the focal point • Back on itself Focal Center

28. For a spherical mirror, light that travels through the focal point reflects • Parallel to the main axis • Through the focal point • Back on itself Center Focal

29. For a spherical mirror, light that travels parallel the the main axis reflects • Parallel to the main axis • Through the focal point • Back on itself Center Focal

30. The boy is looking in the mirror. This mirror is • Concave • Convex

31. The boy is looking in the mirror. This focal length is • Positive • Negative

32. The boy is looking in the lens. This lens is • Concave • Convex

33. The boy is looking in the lens. The focal length is • Positive • Negative

34. Snell’s Law Relates to • Reflection • Refraction • Diffraction • Reflection and Refraction

35. The index of refraction • can never be 1 • can never be greater than 1 • can never be less than 1

36. A high index of refraction corresponds to a • slow speed of light • high speed of light • neither. The speed of light never changes.

37. If a material has an index of refraction of 3.0, what is the speed of light in the material? • 1x108m/s • 2x108m/s • 3x108m/s • 6x108m/s • 9x108m/s

38. air A n=1.5 When going from lower index to higher index, the light bends TOWARD THE NORMAL B Light is incident from air to glass as shown. Which arrow shows the direction of the light in the glass? C D • A • B • C • D

39. n=1.5 A air When going from higher index to lower index, light always bends AWAY FROM THE NORMAL B Light is incident from glass to air as shown. Which arrow shows the direction of the light emerging from the glass? C D • A • B • C • D

40. Total internal reflection can occur when • light travels from air to water • light travels from water to air • either A or B • neither A or B

41. C A Light goes from air to glass as shown. Which arrow shows the path that it will leave the glass? B C D • A • B • C • D

42. refraction reflection refraction When light is incident on the glass, as shown • refraction occurs • reflection occurs • both A and B

43. An object is 1 cm from a glass lens. The image is 2 cm on the other side of the lens. The focal length of the lens is. • 1/3 cm • 2/3 cm • -2/3 cm • 1 cm • 3/2 cm • -3/2 cm

44. The critical angle is 49º for a particular type of glass. Light is incident from the glass to the air at an angle of 48º. Relative to the normal, the exit angle is • Close to 0º • Close to 42º • Close to 48º • Close to 90º

45. If the image distance is a positive number, the image is • real • virtual • upright

46. For a mirror lens, a positive focal length is • concave • convex

47. For a glass lens, a positive focal length is • concave • convex

48. air Light is incident from air to glass. The sin(θ1)=0.6 and thesin(θ2)=0.3. The index of refraction of the glass is θ2 θ1 • 1.0 • 1.5 • 2.0 • 2.5 • 3.0

49. Calcuations you should be able to make • Use the lens equation to solve for image, object, or focal length • Use the magnification formula • Use Snell’s law formula