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Chapter 24 (Geometrical Optics & Instruments)
1. What is the f-number of a camera lens that has an aperture opening diameter of 0.30 cm and a focal length of 3.0 cm?
a. 0.1 b. 0.8 c. 10.0 d. 15.0
2. A camera lens is initially set at f/16 for a shutter speed of 0.016 s. If the amount of lighting on the subject is unchanged and the lens is set at f/5.6, what is the proper shutter speed at this setting?
a. 0.002 s b. 0.004 s c. 0.128 s d. 0.064 s
3. A diverging lens will be prescribed by the eye doctor to correct which of the following?
a. farsightedness b. glaucoma c. nearsightedness d. astigmatism
4. A simple magnifier makes an image appear at the near point distance from the eye of the viewer (25 cm). What is the magnifying power of the magnifier if it is constructed of a lens of focal length of 4.0 cm?
a. 1.20 b. 5.00 c. 7.25 d. 50.0
5. What is the approximate magnification of a compound microscope with objective and eyepiece focal lengths of 0.3 cm and 3.6 cm, respectively, and a separation between lenses of 20 cm?
a. 12 b. 20 c. 67 d. 460
6. A telescope has an objective lens with a focal length of 100 cm and an eyepiece of focal length 3.0 cm. What is the magnification of the telescope?
a. 30 b. 33 c. 60 d. 180
7. Light with a wavelength of 450 nm shines through a lens with an aperture diameter of 0.60 cm. Use Rayleigh’s criterion to determine the limiting angle of resolution.
a. 9.2 ´ 10‑5 rad b. 3.0 ´ 10‑9 rad c. 1.3 ´ 10‑4 rad d. 5.0 ´ 10‑7 rad
8. A multiple slit diffraction grating has a slit separation of 2.0 ´ 10‑6 m . Find the wavelength of the monochromatic light that will have its second order bright fringe diffracted through an angle of 38˚. (1 nm = 10‑9 m)
a. 120 nm b. 500 nm c. 616 nm d. 687 nm
9. The Michelson interferometer is a device that may be used to measure:
a. magnifying power of lenses b. light wavelength c. atomic masses d. electron charge
10. What is the resolving power of a diffraction grating which is capable of just distinguishing between two wavelengths of 568.5 and 569.6 nm?
a. 1.1 b. 517 c. 1035 d. 1.9 ´ 10‑3
11. Tripling the aperture diameter of a camera lens will change the f‑number by what factor?
a. 1/9 b. 1/3 c. 3.0 d. 9.0
12. Tripling the focal length in a telephoto lens, while keeping the aperture size constant, will change the f‑number by what factor?
a. 1/9 b. 1/3 c. 3.0 d. 9.0
13. Doubling the aperture diameter of a camera lens will change the light intensity admitted to the film by what factor?
a. 0.25 b. 0.50 c. 2.0 d. 4.0
14. Doubling the focal length of a telephoto lens, while holding aperture size constant, will change the light intensity admitted to the film by what factor?
a. 0.25 b. 0.50 c. 2.0 d. 4.0
15. Doubling the f‑number of a camera lens will change the light intensity admitted to the film by what factor?
a. 0.25 b. 0.50 c. 2.0 d. 4.0
16 I take two pictures of my dog Kaycee. I use the same film and level of illumination for both pictures, but I double the f‑number for the second picture. By what factor will the required time of exposure change if the film is to receive the same total light energy?
a. 0.25 b. 0.50 c. 2.0 d. 4.0
17. The ciliary muscle is instrumental in changing the shape of which eye part?
a. iris b. lens c. pupil d. retina
18. The ciliary muscle of the eye is relaxed under which condition?
a. eye is focused on a distant object b. eye is focused on a nearby object c. subject being viewed is well illuminated d. subject being viewed is dimly illuminated
19. The pupil of the eye reduces in size under which condition?
a. eye is focused on a distant object b. Eye is focused on a nearby object c. object viewed is well illuminated d. object viewed is dimly illuminated
20. A diverging lens will be prescribed by the eye doctor to correct which of the following?
a. myopia (nearsightedness) b. presbyopia c. hyperopia (farsightedness) d. astigmatism
21. Which term below identifies the eye defect characterized by an inability to see distant objects clearly?
a. myopia b. presbyopia c. hyperopia d. astigmatism
22. Which term identifies the defect where the lens produces a line image of a point source?
a. myopia b. presbyopia c. hyperopia d. astigmatism
23. Which eye defect is corrected by a lens having different curvatures in two perpendicular directions?
a. myopia b. presbyopia c. hyperopia d. astigmatism
24. A lens with a focal length of 20 cm has what power?
a. 5.0 diopters b. 6.7 diopters c. 8.0 diopters d. 9.6 diopters
25. Two thin lenses in combination placed in contact with each other along a common axis, have the respective powers of 45 and ‑15 diopters. What is their combined power?
a. 15 diopters b. 30 diopters c. 60 diopters d. ‑22.5 diopters
26. The “normal” eye has a nearpoint of 25 cm. If a given individual’s nearpoint is 65 cm, for what problem will the eye doctor prescribe correction?
a. myopia (nearsightedness) b. presbyopia (loss of lens flexibility) c. hyperopia (farsightedness) d. astigmatism
27. You are designing eyeglasses for someone whose nearpoint is 60 cm. What focal length lens should you prescribe so that an object can be clearly seen when placed at 25 cm in front of the eye?
a. ‑15 cm b. 18 cm c. 43 cm d. 60 cm
28. A given individual is unable to see objects clearly when they are beyond 100 cm. What focal length lens should be used to correct this problem?
a. ‑100 cm b. ‑33.3 cm c. ‑20 cm d. 75 cm
29. A magnifying lens with a focal length of 10 cm has what maximum magnification? (Assume the nearpoint is 25 cm.)
a. 7.14 b. 2.5 c. 3.0 d. 3.5
30. A magnifying lens with a focal length of 10 cm has what magnification when the viewing eye is relaxed?
a. 7.14 b. 2.5 c. 3.0 d. 3.5
31. You are building a compound microscope with an objective lens focal length of 0.70 cm and an eyepiece lens of 5.0 cm focal length. You mount the lenses 18 cm. What is the maximum magnification of your microscope?
a. 3.1 b. 7.3 c. 67.0 d. 130
32. Tripling the focal length of the objective lens of a compound microscope will change the magnification by what factor?
a. 1/9 b. 1/3 c. 3.0 d. 9.0
33. A refracting astronomical telescope has objective and eyepiece lenses of focal lengths 20 and 0.4 cm, respectively. The separation between the two lenses is 30 cm. What is the magnification of this instrument?
a. 19.6 b. 27.0 c. 50.0 d. 94.0
34. A microscope has an objective lens with an aperture diameter 0.6 cm. A monochromatic light source of 580 nm is used to illuminate the object. It is determined that the minimum angle of resolution is 1.18 ´ 10‑ 4 rad. If the present lens were replaced by one with an aperture of diameter 0.9 cm, what would the minimum angle of resolution now become? (1 nm = 10‑9 m)
a.1.50 ´ 10‑4 rad b.1.77 ´ 10-4 rad c .0.88 ´ 10‑4 rad d. 0.79 ´ 10-4 rad
35. A microscope has an objective lens with an aperture of diameter 0.6 cm where a monochromatic light source of 580 nm is used to illuminate the object. It is determined that the minimum angle of resolution is 1.18 ´ 10-4 rad. If the illuminating source were replaced by an violet source with wavelength of 420 nm, what would the minimum angle of resolution now become? (1 nm = 10‑9 m)
a. 1.63 ´ 10‑4 rad b. 1.18 ´ 10‑4 rad c. 0.85 ´ 10-4 rad d. 0.58 ´ 10‑4 rad
36. An individual’s eye pupil changes from a diameter of 3.5 mm to 1.5 mm as the illumination is increased. By what factor does the minimum angle of resolution change?
a. 0.43 b. 0.65 c. 2.0 d. 2.3
37. A diffraction grating with 10,000 lines/cm will exhibit the first order maximum for light of wavelength 510 nm at what angle? (1 nm = 10‑9 m)
a. 0.51˚ b. 0.62˚ c. 15.3˚ d. 31˚
38. What resolving power must a diffraction grating have in order to distinguish wavelengths of 630.1 and 631.7 nm?
a. 315 b. 394 c. 630.9 d. 788
39. A camera uses a:
a. converging lens to form a real image. b. converging lens to form an imaginary image. c. diverging lens to form a real image. d. diverging lens to form an imaginary image.
40. Changing the f‑number of a camera by two stops by going from f/8 to f/16 will change the brightness of the light hitting the film by:
a. 4. b. 2. c. 1/2. d. 1/4.
41. While a camera has film where the image is formed, the eye forms the image on the:
a. pupil. b. cornea. c. retina. d. optic nerve.
42. The eye changes its f‑number by:
a. using the iris to change the size of the pupil. b. using the ciliary muscle to change the focal length of the lens. c. both a & b are correct d. the eye doesn’t change its f‑number
43. In the normal eye the ciliary muscles that control the lens will relax:
a. when viewing objects at the nearpoint. b. when viewing objects at infinity. c. when viewing objects at a distance of 20 ft. d. only when a person has his/her eyes closed.
44. If a person has hyperopia that person:
a. may have an unusually long eyeball. b. cannot see near objects clearly. c. cannot relax the ciliary muscle adequately. d. can form images behind the retina.
45. A nearsighted person with astigmatism would be prescribed a lens that is:
a. converging only. b. both converging and cylindrical. c. diverging only. d. both diverging and cylindrical.
46. If a person is farsighted the corrective lens will:
a. take an object at the nearpoint and form an image at 25 cm. b. take an object at 25 cm and form an image at the nearpoint. c. take an object at infinity and form an image at 25 cm. d. take an object at infinity and form an image at the nearpoint.
47. Glaucoma occurs because:
a. the eye cannot accommodate properly. b. the shape or size of the eye is not normal. c. there is too much pressure in the fluid in the eyeball. d. the lens is partially or totally opaque.
48. A magnifier uses a:
a. converging lens to form a real image. b. converging lens to form a virtual image. c. diverging lens to form a virtual image. d. diverging lens to form a real image.
49. A compound microscope has an eyepiece that:
a. uses a real image from the objective as the object and forms its own real image. b. uses a real image from the objective as the object and forms a virtual image. c. uses an imaginary image from the objective as the object and forms its own real image. d. uses an imaginary image from the objective as the object and forms its own imaginary image.
50. A 1.7 m tall woman stands 5 m in front of a camera with a 5 cm focal length lens. What is the size of the image formed on film?
a. 3.4 cm b. 2.6 cm c. 1.7 cm d. 0.85 cm
51. A nearsighted person cannot see objects clearly beyond 30 cm (the farpoint). If the patient has no astigmatism and contact lenses are prescribed, what is the power of the lens required to correct the patient's vision?
a. ‑2.0 diopters b. ‑3.3 diopters c. ‑4.0 diopters d. ‑5.0 diopters 52. The pupil of a cat’s eye narrows to a slit of 0.5 mm in daylight. What is the angular resolution? (let l = 500 nm).
a. 10‑3 radians b. 5 ´ 10‑3 radians c. 10‑4 radians d. 5 ´ 10‑4 radians
53. The 2.4 m Hubble space telescope has been placed into Earth orbit by the space shuttle. What angular resolution could this telescope achieve by Rayleigh’s criterion? (l = 500 nm).
a. 7.5 ´ 10‑6 rads b. 5.7 ´ 10‑6 rads c. 3.6 ´ 10‑6 rads d. 2.5 ´ 10‑7 rads
54. A binary star in the constellation Orion has an angular separation between the stars of 10‑5 radians. If l = 500 nm, what is the smallest aperture (diameter) telescope that will just resolve the two stars?
a. 3.0 cm b. 4.2 cm c. 6.1 cm d. 12.6 cm
55. Find the radius of a star image formed on the retina of the eye if the aperture diameter (the pupil) at night is 0.7 cm and the length of the eye is 3.0 cm. Assume the wavelength of starlight in the eye is 500 nm.
a. 2.6 ´ 10‑4 m b. 5.2 ´ 10‑4 m c. 3.1 ´ 10‑5 m d. 2.6 ´ 10‑6 m
56. A helium‑neon laser (l = 632.8 nm) is used to calibrate a diffraction grating. If the first‑order maximum occurs at 20.50˚, what is the line spacing, d?
a. 1.808 ´ 10‑6 m b. 3.616 ´ 10‑6 m c. 5.424 ´ 10‑6 m d. 7.232 ´ 10‑6 m
57. White light is spread out into spectral hues by a diffraction grating. If the grating has 2000 lines per cm, at what angle will red light (l = 640 nm) appear in first order?
a. 3.57˚ b. 7.35˚ c. 11.17˚ d. 13.35˚
58. A lens with focal length 5 cm is used as a magnifying glass. To obtain maximum magnification, how far in front of the lens should the object be placed?
a. 5.00 cm b. 4.16 cm c. 10.0 cm d. 25.0 cm
59. The Yerkes refracting telescope has a 1 m diameter objective lens of focal length 20 m and an eyepiece of focal length 2.5 cm. Determine the magnification of the planet Mars as seen through this telescope.
a. M = 200´ b. M = 400´ c. M = 800´ d. M = l000´
60. The Palomar reflecting telescope has a parabolic mirror with an 80 m focal length. Determine the magnification achieved when an eyepiece of focal length 2.5 cm is used.
a. 800´ b. 1200´ c. 1600´ d. 3200´
Chapter 24 - Answers
# Ans Difficulty # Ans Difficulty 1. C 1 31. D 3 2. A 2 32. B 2 3. C 1 33. C 3 4. C 2 34. D 3 5. D 3 35. C 3 6. B 2 36. D 2 7. A 2 37. D 2 8. C 2 38. B 2 9. B 1 39. A 1 10. B 2 40. D 2 11. B 2 41. C 1 12. C 2 42. C 1 13. D 2 43. B 1 14. A 2 44. B 1 15. A 2 45. D 1 16. D 2 46. B 1 17. B 1 47. C 1 18. A 1 48. B 1 19. C 1 49. B 2 20. A 1 50. C 2 21. A 1 51. B 2 22. D 1 52. A 2 23. D 1 53. D 2 24. A 2 54. C 2 25. B 2 55. D 3 26. C 1 56. A 2 27. C 2 57. B 2 28. A 2 58. B 2 29. D 2 59. C 2 30. B 2 60. D 2
Chapter 24
1. You stand two feet away from a plane mirror. How far is it from you to your image?
a. 2.0 ft b. 3.0 ft c. 4.0 ft d. 5.0 ft
2. The real image of an object is located 45 cm away from a concave mirror (The mirror has a focal length of 10 cm). How far is the object from the mirror?
a. 40.0 cm b. 35.0 cm c. 22.5 cm d. 12.9 cm
3. A concave mirror forms a real image at 25 cm from the mirror surface along the principal axis. If the corresponding object is at a 10 cm distance, what is the mirror’s focal length?
a. 1.4 cm b. 16.7 cm c. 12.4 cm d. 7.1 cm
4. If a virtual image is formed along the principal axis 10 cm from a concave mirror with the focal length 15 cm, what is the object distance from the mirror?
a. 30.0 cm b. 10.0 cm c. 12.4 cm d. 7.1 cm
5. If a virtual image is formed 10 cm along the principal axis from a convex mirror of focal length 15 cm, how far is the object from the mirror?
a. 30.0 cm b. 10.0 cm c. 6.0 cm d. 3.0 cm
6. A woman looking in a makeup mirror sees her face at twice its actual size and right-side up. If she is 28 cm from the mirror, what is its focal length?
a. 18.6 cm b. 44.0 cm c. 48.3 cm d. 56.0 cm 7. Ron fills a beaker with glycerin (n = 1.473) to a depth of 5.0 cm. If he looks straight down through the glycerin surface, he’ll perceive the liquid to be what apparent depth?
a. 7.4 cm b. 5.0 cm c. 3.4 cm d. 1.0 cm
8. A 3 cm tall object is placed along the principal axis of a thin convex lens of 30 cm focal length. If the object distance is 40 cm, which of the following best describes the image distance and height, respectively?
a. 17.3 cm and 7.0 cm b. 120.0 cm and 9.0 cm c. 17.3 cm and 1.3 cm d. 120.0 cm and 1.0 cm
9. Which of the following best describes the image for a thin convex lens that forms whenever the object is at a distance less than one focal length from the lens?
a. inverted, enlarged and real b. upright, enlarged and virtual c. upright, diminished and virtual d. inverted, diminished and real
10. Which of the following best describes the image for a thin concave lens that forms whenever the magnitude of the object distance is less than that of the lens' focal length?
a. inverted, enlarged and real b. upright, enlarged and virtual c. upright, diminished and virtual d. inverted, diminished and real
11. Which of the following best describes the image of a plane mirror?
a. virtual, inverted and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification equal to one d. real, upright and magnification equal to one
12. Which best describes the image of a concave mirror when the object is located somewhere between the focal point and twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one 13. Which of the following best describes the image of a concave mirror when the object is at a distance greater than twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
14. Which of the following best describes the image of a concave mirror when the object’s distance from the mirror is less than the focal point distance?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
15. Which of the following best describes the image of a convex mirror when the object’s distance from the mirror is less than the absolute value of the focal point distance?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
16. An object is placed at a distance of 30 cm from a thin convex lens along its axis. The lens has a focal length of 10 cm. What are the values, respectively, of the image distance and magnification?
a. 60 cm and 2.00 b. 15 cm and 2.00 c. 60 cm and ‑0.50 d. 15 cm and ‑0.50
17. Sally places an object 6 cm from a thin convex lens along its axis. The lens has a focal length of 9 cm. What are the respective values of the image distance and magnification?
a. ‑18 cm and 3 b. 18 cm and 3 c. 3 cm and ‑0.5 d. ‑18 cm and ‑3
18. Ansel places an object 30 cm from a thin convex lens along the axis. If a real image forms at a distance of 10 cm from the lens, what is the focal length of the lens?
a. 30 cm b. 15 cm c. 10 cm d. 7.5 cm 19. An object is placed at a distance of 40 cm from a thin lens along the axis. If a virtual image forms at a distance of 50 cm from the lens, on the same side as the object, what is the focal length of the lens?
a. 22 cm b. 45 cm c. 90 cm d. 200 cm
20. Ellen places an object 40 cm from a concave lens. If a virtual image appears 10 cm from the lens on the same side as the object, what is the focal length of the lens?
a. ‑50.0 cm b. ‑13.3 cm c. ‑10.0 cm d. ‑8.0 cm
21. Atmospheric refraction of light rays is responsible for:
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
22. Which of the following effects is the result of the fact that the index of refraction of glass will vary with wavelength?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
23. In an ideal case rays coming from an object toward a lens or mirror should be reasonably close to the optic axis. To the extent that this condition is not completely met, which one of the following effects occurs?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
24. A fused combination of a diverging and converging lens pair each made from a different index of refraction glass, is used to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
25. Reducing the lens aperture size is a scheme one can use to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
26. Use of a parabolic mirror, instead of one made of a circular arc surface, can be used to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
27. A solid glass sphere with a radius of 5.0 cm and index of refraction of 1.52 has a small coin embedded 3.0 cm from the front surface of the sphere. For the viewer looking at the coin through the glass, at what distance from the front surface of the glass does the coin’s image appear to be located?
a. 2.48 cm b. 3.20 cm c. 5.00 cm d. 6.85 cm
28. Two thin lenses of focal lengths 15 and 20 cm, respectively, are placed in contact in an orientation so that their optic axes coincide. What is the focal length of the two in combination?
a. 8.57 cm b. 17.5 cm c. 35 cm d. 60 cm
29. Two thin lenses, with focal lengths of 25 and ‑30 cm, respectively, are placed in contact orientated so that their optic axes coincide. What is the effective focal length of the two in combination?
a. ‑2.5 cm b. 13.6 cm c. 55 cm d. 150 cm
30. A glass block, for which n = 1.48, has a bubble blemish located 6.4 cm from one surface. At what distance from that surface does the image of the blemish appear to the outside observer?
a. 3.2 cm b. 4.3 cm c. 7.6 cm d. 9.5 cm
31. Two thin lenses with 10 cm focal lengths at are mounted at opposite ends of a 30 cm long tube. An object is located 45 cm from one end of the tube. How far from the opposite end is the final image?
a. 12.8 cm b. 24.0 cm c. 25.6 cm d. 33.6 cm
32. A convex mirror with focal length of ‑20 cm forms an image 12 cm behind the surface. Where is the object located as measured from the surface?
a. 7.5 cm b. 15 cm c. 22 cm d. 30 cm
33. A convex mirror with a focal length of ‑20 cm forms an image 15 cm behind the surface. If the object height is 1.2 cm what is the image height?
a. 0.30 cm b. 0.75 cm c. 0.94 cm d. 3.0 cm
34. An object placed 12 cm from a concave mirror produces a real image 8 cm from the mirror. If the object is now moved to a new position 18 cm from the mirror, where is the new image located as measured from the mirror?
a. 3.0 cm b. 6.5 cm c. 9.2 cm d. 14.6 cm
35. A projector lens is needed to form an image on a screen 10 times the size of its corresponding object. The screen is located 8 m from the lens. What is the required focal length of the lens?
a. 0.32 m b. 0.54 m c. 0.73 m d. 1.12 m
36. An object, located 90 cm from a concave lens, forms an image 60 cm from and on the same side of that lens. What is the focal length of the lens?
a. ‑36 cm b. ‑75 cm c. -180 cm d. ‑150 cm 37. An object is held at a distance of 12 cm from a convex mirror creating a resultant image that is 1/3 the object size. What is the focal length of the mirror?
a. ‑6.0 cm b. ‑3.0 cm c. ‑9.0 cm d. ‑18.0 cm
38. Two convex thin lenses with focal lengths 10 and 20 cm, respectively, are aligned on a common axis, running left to right, the 10 cm lens being on the left. The lenses are separated by a distance of 20 cm. An object is located at a distance of 15 cm to the left of the 10 cm lens. Where will the final image appear as measured from the 20 cm lens?
a. ‑13.3 cm b. ‑6.67 cm c. +6.67 cm d. +13.3 cm
39. When the reflection of an object is seen in a plane mirror, the image is:
a. real and upright. b. real and inverted. c. virtual and upright. d. virtual and inverted.
40. When the reflection of an object is seen in a plane mirror, the distance from the mirror to the image depends on:
a. the wavelength of light used for viewing. b. the distance from the object to the mirror. c. the distance of both the observer and the object to the mirror. d. the size of the object.
41. If a man wishes to use a plane mirror on a wall to view both his head and his feet as he stands in front of the mirror, the required length of the mirror:
a. is equal to the height of the man. b. is equal to one half the height of the man. c. depends on the distance the man stands from the mirror. d. depends on both the height of the man and the distance from the man to the mirror.
42. When the reflection of an object is seen in a concave mirror the image will:
a. always be real. b. always be virtual. c. may be either real or virtual. d. will always be magnified.
43. When the reflection of an object is seen in a convex mirror the image will:
a. always be real. b. always be virtual. c. may be either real or virtual. d. will always be magnified.
44. Parallel rays of light that hit a concave mirror will come together:
a. at the center of curvature. b. at the focal point. c. at a point half way to the focal point. d. at infinity.
45. A girl is standing in front of a concave mirror. Consider two rays of light, one from her nose and one from her mouth, that are parallel as they are traveling toward the mirror. These rays will come together:
a. at the focal point. b. at the center of curvature. c. at the image point. d. behind the mirror if she is too close to the mirror.
46. If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed?
a. both would be later b. both would be earlier c. sunrise would be later and sunset earlier d. sunrise would be earlier and sunset later
47. An object and a screen are separated by 20 cm. A convex lens is placed between them, 5 cm from the object. In this position it causes a sharp image of the object to form on the screen. What is the focal length of the lens?
a. 15 cm b. 5.0 cm c. 3.75 cm d. 2.0 cm
48. For a converging lens with two curved surfaces, the radius of curvature for both surfaces is 10 cm. If the focal length is 10 cm, what must the index of refraction be?
a. 1.5 b. 2.0 c. 2.5 d. 3.0 49. For a diverging lens with one flat surface, the radius of curvature for the curved surface is 10 cm. What must the index of refraction be so that the focal length is ‑10 cm?
a. 1.5 b. 2.0 c. 3.0 d. 0.5
50. A converging lens with two curved surfaces has a front surface with radius of curvature = 10 cm; the back surface has radius of curvature = 20 cm and it is made from material with an index of refraction of 2.5. What is the focal length of the lens?
a. 4.4 cm b. 13.3 cm c. ‑13.3 cm d. 0.25 cm
51. A candle is 49 cm in front of a convex spherical mirror of radius of curvature 70 cm. Where is the image and what is its magnification?
a. q = ‑20.4 cm, M = +0.417 b. q = +20.4 cm, M = ‑0.417 c. q = 122.5 cm, M =+2.50 d. q = ‑20.4 cm, M = ‑0.417
52. An object 2 cm high is placed 10 cm in front of a mirror. What type of mirror and what radius of curvature is needed for an image that is upright and 4 cm tall?
a. Concave, R = 20 cm b. Concave, R = 40 cm c. Convex, R = ‑10 cm d. Convex, R = ‑20 cm
53. An object is 15 cm from the surface of a spherical Christmas tree ornament that is 5 cm in diameter. What is the magnification of the image?
a. ‑0.055 b. +0.033 c. +0.077 d. +0.154
54. A goldfish is swimming in water (n = 1.33) inside a spherical plastic bowl of index of refraction 1.33. If the goldfish is 10 cm from the front wall of the 15 cm radius bowl, where does the goldfish appear to an observer in front of the bowl?
a. q = ‑6 cm b. q = ‑7 cm c. q = ‑8 cm d. q = ‑9 cm 55. What is the image location of an object 1 m in front of a converging lens of focal length 20 cm?
a. q = +16.7 cm b. q = +20.0 cm c. q = +25.0 cm d. q = +33.3 cm
56. A magnifying glass has a convex lens of focal length 15 cm. At what distance from a postage stamp should you hold this lens to get a magnification of +2?
a. 10.0 cm b. 7.5 cm c. 5.0 cm d. 2.5 cm
57. A contact lens is made of plastic with an index of refraction 1.50. The lens has an outer radius of curvature of +2.0 cm and an inner radius of curvature of +2.5 cm. What is its focal length?
a. ‑20 cm b.+6.67 cm c. +10 cm d. +20 cm
Chapter 24 (Mirror's & Lenses)
ML1. You stand two feet away from a plane mirror. How far is it from you to your image?
a. 2.0 ft b. 3.0 ft c. 4.0 ft d. 5.0 ft
ML2. The real image of an object is located 45 cm away from a concave mirror (The mirror has a focal length of 10 cm). How far is the object from the mirror?
a. 40.0 cm b. 35.0 cm c. 22.5 cm d. 12.9 cm
ML3. A concave mirror forms a real image at 25 cm from the mirror surface along the principal axis. If the corresponding object is at a 10 cm distance, what is the mirror’s focal length?
a. 1.4 cm b. 16.7 cm c. 12.4 cm d. 7.1 cm
ML4. If a virtual image is formed along the principal axis 10 cm from a concave mirror with the focal length 15 cm, what is the object distance from the mirror?
a. 30.0 cm b. 10.0 cm c. 12.4 cm d. 7.1 cm
ML5. If a virtual image is formed 10 cm along the principal axis from a convex mirror of focal length 15 cm, how far is the object from the mirror?
a. 30.0 cm b. 10.0 cm c. 6.0 cm d. 3.0 cm
ML6. A woman looking in a makeup mirror sees her face at twice its actual size and right-side up. If she is 28 cm from the mirror, what is its focal length?
a. 18.6 cm b. 44.0 cm c. 48.3 cm d. 56.0 cm ML7. Ron fills a beaker with glycerin (n = 1.473) to a depth of 5.0 cm. If he looks straight down through the glycerin surface, he’ll perceive the liquid to be what apparent depth?
a. 7.4 cm b. 5.0 cm c. 3.4 cm d. 1.0 cm
ML8. A 3 cm tall object is placed along the principal axis of a thin convex lens of 30 cm focal length. If the object distance is 40 cm, which of the following best describes the image distance and height, respectively?
a. 17.3 cm and 7.0 cm b. 120.0 cm and 9.0 cm c. 17.3 cm and 1.3 cm d. 120.0 cm and 1.0 cm
ML9. Which of the following best describes the image for a thin convex lens that forms whenever the object is at a distance less than one focal length from the lens?
a. inverted, enlarged and real b. upright, enlarged and virtual c. upright, diminished and virtual d. inverted, diminished and real
ML10. Which of the following best describes the image for a thin concave lens that forms whenever the magnitude of the object distance is less than that of the lens' focal length?
a. inverted, enlarged and real b. upright, enlarged and virtual c. upright, diminished and virtual d. inverted, diminished and real
ML11. Which of the following best describes the image of a plane mirror?
a. virtual, inverted and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification equal to one d. real, upright and magnification equal to one
ML12. Which best describes the image of a concave mirror when the object is located somewhere between the focal point and twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one ML13. Which of the following best describes the image of a concave mirror when the object is at a distance greater than twice the focal point distance from the mirror?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
ML14. Which of the following best describes the image of a concave mirror when the object’s distance from the mirror is less than the focal point distance?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
ML15. Which of the following best describes the image of a convex mirror when the object’s distance from the mirror is less than the absolute value of the focal point distance?
a. virtual, upright and magnification greater than one b. real, inverted and magnification less than one c. virtual, upright and magnification less than one d. real, inverted and magnification greater than one
ML16. An object is placed at a distance of 30 cm from a thin convex lens along its axis. The lens has a focal length of 10 cm. What are the values, respectively, of the image distance and magnification?
a. 60 cm and 2.00 b. 15 cm and 2.00 c. 60 cm and ‑0.50 d. 15 cm and ‑0.50
ML17. Sally places an object 6 cm from a thin convex lens along its axis. The lens has a focal length of 9 cm. What are the respective values of the image distance and magnification?
a. ‑18 cm and 3 b. 18 cm and 3 c. 3 cm and ‑0.5 d. ‑18 cm and ‑3
ML18. Ansel places an object 30 cm from a thin convex lens along the axis. If a real image forms at a distance of 10 cm from the lens, what is the focal length of the lens?
a. 30 cm b. 15 cm c. 10 cm d. 7.5 cm ML19. An object is placed at a distance of 40 cm from a thin lens along the axis. If a virtual image forms at a distance of 50 cm from the lens, on the same side as the object, what is the focal length of the lens?
a. 22 cm b. 45 cm c. 90 cm d. 200 cm
ML20. Ellen places an object 40 cm from a concave lens. If a virtual image appears 10 cm from the lens on the same side as the object, what is the focal length of the lens?
a. ‑50.0 cm b. ‑13.3 cm c. ‑10.0 cm d. ‑8.0 cm
ML21. Atmospheric refraction of light rays is responsible for:
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML22. Which of the following effects is the result of the fact that the index of refraction of glass will vary with wavelength?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML23. In an ideal case rays coming from an object toward a lens or mirror should be reasonably close to the optic axis. To the extent that this condition is not completely met, which one of the following effects occurs?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML24. A fused combination of a diverging and converging lens pair each made from a different index of refraction glass, is used to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML25. Reducing the lens aperture size is a scheme one can use to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML26. Use of a parabolic mirror, instead of one made of a circular arc surface, can be used to reduce the occurrence of which of the following effects?
a. spherical aberration b. mirages c. chromatic aberration d. light scattering
ML27. A solid glass sphere with a radius of 5.0 cm and index of refraction of 1.52 has a small coin embedded 3.0 cm from the front surface of the sphere. For the viewer looking at the coin through the glass, at what distance from the front surface of the glass does the coin’s image appear to be located?
a. 2.48 cm b. 3.20 cm c. 5.00 cm d. 6.85 cm
ML28. Two thin lenses of focal lengths 15 and 20 cm, respectively, are placed in contact in an orientation so that their optic axes coincide. What is the focal length of the two in combination?
a. 8.57 cm b. 17.5 cm c. 35 cm d. 60 cm
ML29. Two thin lenses, with focal lengths of 25 and ‑30 cm, respectively, are placed in contact orientated so that their optic axes coincide. What is the effective focal length of the two in combination?
a. ‑2.5 cm b. 13.6 cm c. 55 cm d. 150 cm
ML30. A glass block, for which n = 1.48, has a bubble blemish located 6.4 cm from one surface. At what distance from that surface does the image of the blemish appear to the outside observer?
a. 3.2 cm b. 4.3 cm c. 7.6 cm d. 9.5 cm
ML31. Two thin lenses with 10 cm focal lengths at are mounted at opposite ends of a 30 cm long tube. An object is located 45 cm from one end of the tube. How far from the opposite end is the final image?
a. 12.8 cm b. 24.0 cm c. 25.6 cm d. 33.6 cm
ML32. A convex mirror with focal length of ‑20 cm forms an image 12 cm behind the surface. Where is the object located as measured from the surface?
a. 7.5 cm b. 15 cm c. 22 cm d. 30 cm
ML33. A convex mirror with a focal length of ‑20 cm forms an image 15 cm behind the surface. If the object height is 1.2 cm what is the image height?
a. 0.30 cm b. 0.75 cm c. 0.94 cm d. 3.0 cm
ML34. An object placed 12 cm from a concave mirror produces a real image 8 cm from the mirror. If the object is now moved to a new position 18 cm from the mirror, where is the new image located as measured from the mirror?
a. 3.0 cm b. 6.5 cm c. 9.2 cm d. 14.6 cm
ML35. A projector lens is needed to form an image on a screen 10 times the size of its corresponding object. The screen is located 8 m from the lens. What is the required focal length of the lens?
a. 0.32 m b. 0.54 m c. 0.73 m d. 1.12 m
ML36. An object, located 90 cm from a concave lens, forms an image 60 cm from and on the same side of that lens. What is the focal length of the lens?
a. ‑36 cm b. ‑75 cm c. -180 cm d. ‑150 cm ML37. An object is held at a distance of 12 cm from a convex mirror creating a resultant image that is 1/3 the object size. What is the focal length of the mirror?
a. ‑6.0 cm b. ‑3.0 cm c. ‑9.0 cm d. ‑18.0 cm
ML38. Two convex thin lenses with focal lengths 10 and 20 cm, respectively, are aligned on a common axis, running left to right, the 10 cm lens being on the left. The lenses are separated by a distance of 20 cm. An object is located at a distance of 15 cm to the left of the 10 cm lens. Where will the final image appear as measured from the 20 cm lens?
a. ‑13.3 cm b. ‑6.67 cm c. +6.67 cm d. +13.3 cm
ML39. When the reflection of an object is seen in a plane mirror, the image is:
a. real and upright. b. real and inverted. c. virtual and upright. d. virtual and inverted.
ML40. When the reflection of an object is seen in a plane mirror, the distance from the mirror to the image depends on:
a. the wavelength of light used for viewing. b. the distance from the object to the mirror. c. the distance of both the observer and the object to the mirror. d. the size of the object.
ML41. If a man wishes to use a plane mirror on a wall to view both his head and his feet as he stands in front of the mirror, the required length of the mirror:
a. is equal to the height of the man. b. is equal to one half the height of the man. c. depends on the distance the man stands from the mirror. d. depends on both the height of the man and the distance from the man to the mirror.
ML42. When the reflection of an object is seen in a concave mirror the image will:
a. always be real. b. always be virtual. c. may be either real or virtual. d. will always be magnified.
ML43. When the reflection of an object is seen in a convex mirror the image will:
a. always be real. b. always be virtual. c. may be either real or virtual. d. will always be magnified.
ML44. Parallel rays of light that hit a concave mirror will come together:
a. at the center of curvature. b. at the focal point. c. at a point half way to the focal point. d. at infinity.
ML45. A girl is standing in front of a concave mirror. Consider two rays of light, one from her nose and one from her mouth, that are parallel as they are traveling toward the mirror. These rays will come together:
a. at the focal point. b. at the center of curvature. c. at the image point. d. behind the mirror if she is too close to the mirror.
ML46. If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed?
a. both would be later b. both would be earlier c. sunrise would be later and sunset earlier d. sunrise would be earlier and sunset later
ML47. An object and a screen are separated by 20 cm. A convex lens is placed between them, 5 cm from the object. In this position it causes a sharp image of the object to form on the screen. What is the focal length of the lens?
a. 15 cm b. 5.0 cm c. 3.75 cm d. 2.0 cm
ML48. For a converging lens with two curved surfaces, the radius of curvature for both surfaces is 10 cm. If the focal length is 10 cm, what must the index of refraction be?
a. 1.5 b. 2.0 c. 2.5 d. 3.0 ML49. For a diverging lens with one flat surface, the radius of curvature for the curved surface is 10 cm. What must the index of refraction be so that the focal length is ‑10 cm?
a. 1.5 b. 2.0 c. 3.0 d. 0.5
ML50. A converging lens with two curved surfaces has a front surface with radius of curvature = 10 cm; the back surface has radius of curvature = 20 cm and it is made from material with an index of refraction of 2.5. What is the focal length of the lens?
a. 4.4 cm b. 13.3 cm c. ‑13.3 cm d. 0.25 cm
ML51. A candle is 49 cm in front of a convex spherical mirror of radius of curvature 70 cm. Where is the image and what is its magnification?
a. q = ‑20.4 cm, M = +0.417 b. q = +20.4 cm, M = ‑0.417 c. q = 122.5 cm, M =+2.50 d. q = ‑20.4 cm, M = ‑0.417
ML52. An object 2 cm high is placed 10 cm in front of a mirror. What type of mirror and what radius of curvature is needed for an image that is upright and 4 cm tall?
a. Concave, R = 20 cm b. Concave, R = 40 cm c. Convex, R = ‑10 cm d. Convex, R = ‑20 cm
ML53. An object is 15 cm from the surface of a spherical Christmas tree ornament that is 5 cm in diameter. What is the magnification of the image?
a. ‑0.055 b. +0.033 c. +0.077 d. +0.154
ML54. A goldfish is swimming in water (n = 1.33) inside a spherical plastic bowl of index of refraction 1.33. If the goldfish is 10 cm from the front wall of the 15 cm radius bowl, where does the goldfish appear to an observer in front of the bowl?
a. q = ‑6 cm b. q = ‑7 cm c. q = ‑8 cm d. q = ‑9 cm ML55. What is the image location of an object 1 m in front of a converging lens of focal length 20 cm?
a. q = +16.7 cm b. q = +20.0 cm c. q = +25.0 cm d. q = +33.3 cm
ML56. A magnifying glass has a convex lens of focal length 15 cm. At what distance from a postage stamp should you hold this lens to get a magnification of +2?
a. 10.0 cm b. 7.5 cm c. 5.0 cm d. 2.5 cm
ML57. A contact lens is made of plastic with an index of refraction 1.50. The lens has an outer radius of curvature of +2.0 cm and an inner radius of curvature of +2.5 cm. What is its focal length?
a. ‑20 cm b.+6.67 cm c. +10 cm d. +20 cm
Chapter 24 (Geometrical Optics & Instruments)
- Answers
# Ans Difficulty # Ans Difficulty 1. C 1 30. B 2 2. B 2 31. B 3 3. D 2 32. D 2 4. C 2 33. A 2 5. A 2 34. B 2 6. D 2 35. C 2 7. C 1 36. C 2 8. B 2 37. A 2 9. B 2 38. C 3 10. C 2 39. C 1 11. C 1 40. B 1 12. D 2 41. B 1 13. B 2 42. C 1 14. A 2 43. B 1 15. C 2 44. B 1 16. D 2 45. A 1 17. A 2 46. C 1 18. D 2 47. C 2 19. D 2 48. A 2 20. B 2 49. B 2 21. B 1 50. A 3 22. C 1 51. A 2 23. A 1 52. B 2 24. C 1 53. C 2 25. A 1 54. D 3 26. A 1 55. C 2 27. A 3 56. B 2 28. A 3 57. D 3 29. D 3
Chapter 24: mIRROR'S & lenses' (ml)- Answers
# Ans Difficulty # Ans Difficulty ML1. C 1 ML30. B 2 ML2. B 2 ML31. B 3 3. D 2 32. D 2 4. C 2 33. A 2 5. A 2 34. B 2 6. D 2 35. C 2 7. C 1 36. C 2 8. B 2 37. A 2 9. B 2 38. C 3 10. C 2 39. C 1 11. C 1 40. B 1 12. D 2 41. B 1 13. B 2 42. C 1 14. A 2 43. B 1 15. C 2 44. B 1 16. D 2 45. A 1 17. A 2 46. C 1 18. D 2 47. C 2 19. D 2 48. A 2 20. B 2 49. B 2 21. B 1 50. A 3 22. C 1 51. A 2 23. A 1 52. B 2 24. C 1 53. C 2 25. A 1 54. D 3 26. A 1 55. C 2 27. A 3 56. B 2 28. A 3 57. D 3 29. D 3
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