2) A convex lens is known as a diverging lens and a concave lens is known as a converging lens. Answer: FALSE Diff: 1 Var: 1 Page Ref: Sec.

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1 Physics for Scientists and Engineers, 4e (Giancoli) Chapter 33 Lenses and Optical Instruments 33.1 Conceptual Questions 1) State how to draw the three rays for finding the image position due to a thin lens. Answer: Ray 1 leaves the top of the object and is drawn such that it is parallel to the axis; therefore it emerges from the lens along a line through the focal point on the back side of the lens. Ray 2 leaves the top of the object and is made to pass through the other focal point; therefore it emerges from the lens parallel to the axis. Ray 3 leaves the top of the object and is directed toward the very center of the lens; therefore it emerges from the lens at the same angle as it entered. Diff: 2 Var: 1 Page Ref: Sec ) A convex lens is known as a diverging lens and a concave lens is known as a converging lens. Answer: FALSE 3) A convex lens always produces a virtual image. Answer: FALSE 4) A concave lens always produces a virtual image. 5) The difference between a camera and the human eye is that a camera utilizes a fixed focal length lens and the eye does not. 6) The near point of a normal human eye is infinity. Answer: FALSE 7) The far point of a normal human eye is infinity. 8) The process of changing the shape of the lens, and hence adjusting its focal length, is referred as accommodation. 9) Nearsightedness can be corrected with a diverging lens. 10) Farsightedness can be corrected with a converging lens. 1

2 11) In a nearsighted person the eye makes the light coming into it converge too rapidly. 12) A person with a longer near point can see an object as closely with the unaided eye as can a person with the shorter near point. Answer: FALSE 13) A magnifying glass produces a virtual image. Diff: 1 Var: 1 Page Ref: Sec ) A magnifying glass can be made from a diverging lens. Answer: FALSE Diff: 1 Var: 1 Page Ref: Sec ) A diverging lens cannot be used as a magnifying glass. Diff: 1 Var: 1 Page Ref: Sec ) The refractive power of a lens used as a magnifying glass is negative. Answer: FALSE Diff: 2 Var: 1 Page Ref: Sec ) In a compound microscope the final image is virtual. Diff: 1 Var: 1 Page Ref: Sec ) The focal length of the objective in a microscope is very small as compared to the focal length of the eyepiece. Diff: 1 Var: 1 Page Ref: Sec ) The focal length of the objective of a telescope is much longer than the focal length of the eyepiece. Diff: 2 Var: 1 Page Ref: Sec ) Chromatic aberration can be corrected by combining two or more lenses to form a compound lens. 0 21) Of the following lenses, which is not a converging lens? A) concave meniscus B) planoconcave C) double convex D) planoconvex E) All of the above are not converging lenses. 2

3 22) A light ray, traveling parallel to the axis of a thin concave lens, strikes the lens near its midpoint. After traveling though the lens, this ray emerges traveling obliquely to the axis of the lens A) such that it never crosses the axis. B) crossing the axis at a point equal to twice the focal length. C) crossing the axis at a point equal to one-half the focal length. D) passing between the lens and its focal point. E) passing through the focal point. 23) A light ray, traveling parallel to the axis of a convex thin lens, strikes the lens near its midpoint. After traveling through the lens, this ray emerges traveling obliquely to the axis of the lens A) such that it never crosses the axis. B) crossing the axis at a point equal to twice the focal length. C) crossing the axis at a point equal to one-half the focal length. D) passing between the lens and its focal point. E) passing through its focal point. 24) A convex lens has focal length f. An object is located at infinity. The image formed is located A) at infinity. B) at 2f. C) between f and 2f. D) at f. E) between the lens and f. 25) A convex lens has a focal length f. An object is placed at f on the axis. The image formed is located A) at infinity. B) between 2f and infinity. C) at 2f. D) between f and 2f. E) between the lens and f. 26) A convex lens has focal length f. An object is placed at 2f on the axis. The image formed is located A) between 2f and infinity. B) at 2f. C) between f and 2f. D) at f. 3

4 27) A convex lens has a focal length f. An object is placed between f and 2f on the axis. The image formed is located A) at 2f. B) between f and 2f. C) at f. D) between the lens and f. E) at a distance greater than 2f from the lens. 28) A convex lens has a focal length f. An object is placed between infinity and 2f from the lens on its axis. The image formed is located A) at a distance greater than 2f from the lens. B) at 2f. C) between f and 2f. D) at f. E) between the lens and f. 29) In calculating the lateral magnification from a lens, a negative result means A) the image is larger than the object. B) the image is smaller than the object. C) the image is directed downward. D) the image is inverted. E) the calculation is incorrect. Diff: 1 Var: 1 Page Ref: Sec ) Select which statement is correct in describing the image formed by a thin lens of a real object placed in front of the lens. A) If the lens is convex, the image will never be virtual. B) If the image is real, then it is also inverted. C) If the image is real, then it is also upright. D) If the image is virtual, then it is also inverted. Diff: 1 Var: 1 Page Ref: Sec ) The images formed by concave lenses A) are always real. B) are always virtual. C) could be real or virtual; it depends on whether the object distance is smaller or greater than the focal length. D) could be real or virtual, but always real when the object is placed at the focal point. Diff: 2 Var: 1 Page Ref: Sec

5 32) The image formed by convex lenses are A) always upright. B) always real. C) always virtual. D) always inverted. E) none of the above. Diff: 2 Var: 1 Page Ref: Sec ) A lens of focal length 20 cm has an object of height 3.0 cm placed 100 cm in front of it. The image formed is A) upright and smaller than the object. B) inverted and smaller than the object. C) inverted and larger than the object. D) upright and larger than the object. E) upright and the same size as the object. Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 35 cm beyond the first, this second lens having a focal length of 8.0 cm. The final image A) is virtual and upright. B) is real and upright. C) is virtual and inverted. D) is real and inverted. E) cannot be determined with the information given. Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 15 cm past the first lens. The second lens has a focal length of 40 cm. The final image A) is real and upright. B) is virtual and upright. C) is real and inverted. D) is virtual and inverted. E) cannot be determined with the information given. Diff: 2 Var: 1 Page Ref: Sec ) The length of time the shutter is open when the film is exposed in a camera is determined by the A) shutter speed. B) f-stop. C) focal length of the lens. D) focusing. E) diameter of the aperature. Diff: 1 Var: 1 Page Ref: Sec

6 37) The amount of light reaching the film in a camera is determined by the A) shutter speed. B) f-stop. C) focal length of the lens. D) focusing. E) diameter of the aperature. Diff: 1 Var: 1 Page Ref: Sec ) A camera lens that covers the film with a field of view that corresponds approximately to that of normal vision is referred to as a A) normal lens. B) telephoto lens. C) wide-angle lens. D) zoom lens. E) digital lens. Diff: 1 Var: 1 Page Ref: Sec ) A camera lens that acts like a telescope to magnify images is referred to as a A) normal lens. B) telephoto lens. C) wide-angle lens. D) zoom lens. E) digital lens. Diff: 1 Var: 1 Page Ref: Sec ) A camera lens that covers the film with a wider field of view than that of the eye and through which objects appear smaller is referred to as a A) normal lens. B) telephoto lens. C) wide-angle lens. D) zoom lens. E) digital lens. Diff: 1 Var: 1 Page Ref: Sec ) The principal refraction of light by the eye occurs at the A) cornea. B) lens. C) retina. D) iris. E) optical nerve. 6

7 42) If a person's eyeball is too long from front to back, the person is likely to suffer from A) spherical aberration. B) chromatic aberration. C) nearsightedness. D) farsightedness. E) astigmatism. 43) If a person's eyeball is too short from front to back, the person is likely to suffer from A) astigmatism. B) spherical aberration. C) chromatic aberration. D) farsightedness. E) nearsightedness. 44) Nearsightedness can usually be corrected with A) converging lenses. B) diverging lenses. C) achromatic lenses. D) cylindrical lenses. E) spherical lenses. 45) Farsightedness can usually be corrected with A) cylindrical lenses. B) achromatic lenses. C) diverging lenses. D) converging lenses. E) spherical lenses. 46) What type of lens is a magnifying glass? A) converging B) diverging C) spherical D) cylindrical E) achromatic Diff: 1 Var: 1 Page Ref: Sec ) The image of the rare stamp you see through a magnifying glass is A) always the same orientation as the stamp. B) always upside-down compared to the stamp. C) either the same orientation or upside-down, depending on how close the stamp is to the glass. D) either the same orientation or upside-down, depending on the thickness of the glass used. E) either the same orientation or upside-down, depending on the diameter of the glass used. Diff: 2 Var: 1 Page Ref: Sec

8 48) Which one of the following is not a characteristic of a simple two-lens astronomical refracting telescope? A) The angular size of the final image is larger than that of the object. B) The final image is virtual. C) The objective forms a virtual image. D) The final image is inverted. Diff: 1 Var: 1 Page Ref: Sec ) An important reason for using a very large diameter objective in an astronomical telescope is A) to increase the magnification. B) to increase the resolution. C) to form a virtual image, which is easier to look at. D) to increase the width of the field of view. E) to increase the depth of the field of view. Diff: 1 Var: 1 Page Ref: Sec ) A simple refracting telescope provides large magnification by employing A) a short focal length objective and a short focal length eyepiece. B) a short focal length objective and a long focal length eyepiece. C) a long focal length objective and a short focal length eyepiece. D) a long focal length objective and a long focal length eyepiece. Diff: 1 Var: 1 Page Ref: Sec ) The objectives of two astronomical telescopes have the same focal length but one objective has double the diameter of the other. An advantage of the telescope with the larger objective is A) its higher power. B) its greater aberration. C) its higher price. D) its brighter image. E) its lower aberration. Diff: 1 Var: 1 Page Ref: Sec ) Consider the image formed by a refracting telescope. Suppose an opaque screen is placed in front of the lower half of the objective lens. What effect will this have? A) The top half of the image will be blacked out. B) The lower half of the image will be blacked out. C) The entire image will be blacked out, since the entire lens is needed to form an image. D) The image will appear as it would if the objective were not blocked, but it will be dimmer. E) There will be no noticeable difference in the appearance of the image with the objective partially blocked or not. Diff: 2 Var: 1 Page Ref: Sec ) A simple compound microscope provides large magnification by employing A) a short focal length objective and a short focal length eyepiece. B) a short focal length objective and a long focal length eyepiece. C) a long focal length objective and a short focal length eyepiece. D) a long focal length objective and a long focal length eyepiece. Diff: 1 Var: 1 Page Ref: Sec

9 54) Which one of the following is a characteristic of a compound microscope? A) The objective is a diverging lens. B) The eyepiece is a diverging lens. C) The final image is real. D) The image formed by the objective is virtual. E) The image formed by the objective is real. Diff: 1 Var: 1 Page Ref: Sec ) You are given two converging lenses to build a compound microscope. Lens A has focal length 0.50 cm and lens B has focal length of 3.0 cm. Which of the two lenses would you use for the objective? A) Lens A, because it has the shorter focal length. B) Lens B, because it has the longer focal length. C) It makes no difference which lens I use for the objective. D) None, because the objective should be a diverging lens. Diff: 1 Var: 1 Page Ref: Sec ) The deviation of a lens from its ideal behavior is referred to as A) spherical aberration. B) chromatic aberration. C) an aberration. D) achromatic aberration. E) None of the other choices is correct. 0 57) The chromatic aberration in lenses is due to the A) reflection of light by the lens. B) refraction of light by the lens. C) dispersion of light by the lens. D) polarization of light by the lens. E) None of the other choices is correct. 0 58) Spherical lenses suffer from A) both spherical and chromatic aberration. B) spherical aberration, but not chromatic aberration. C) chromatic aberration, but not spherical aberration. D) neither spherical nor chromatic aberration. 0 59) Spherical mirrors suffer from A) both spherical and chromatic aberration. B) spherical aberration, but not chromatic aberration. C) chromatic aberration, but not spherical aberration. D) neither spherical nor chromatic aberration. 0 9

10 60) Which one of the following is true regarding spherical aberration? A) It is related to the focal length of the lens. B) It is related to the diameter of the lens. C) It is related to the dispersion of light through the lens. D) It is related to the medium in which a lens is placed. E) It is related to the shape of the lens. Diff: 2 Var: 1 Page Ref: Sec ) Do mirrors suffer from chromatic aberration? A) Yes, every optical instrument suffers from it. B) Yes, because of their specular dispersion. C) No, because the angle of reflection is always equal to the angle of incidence. D) None of the previous choices is correct. Diff: 2 Var: 1 Page Ref: Sec Quantitative Problems 1) A person's eye lens is 2.7 cm away from the retina. (a) What must the focal length of this lens be in order for an object placed at the near point (N = 25.0 cm) of the eye to focus on the retina? (b) What must the focal length of this lens be in order for an object placed at the far point of the eye to focus on the retina? Answer: (a) 2.4 cm (b) 2.7 cm Diff: 2 Var: 5 Page Ref: Sec ) A person uses a converging lens of focal length 5.0 cm as a magnifying glass. (a) What is the magnification if the person's eye is relaxed? (b) What is the maximum possible magnification? Answer: (a) 5.0 (b) 6.0 Diff: 2 Var: 1 Page Ref: Sec ) A magnifying lens has a focal length of 10 cm. A person has a near point of 25 cm. (a) What is the magnification of the lens for that person when their eyes are focused at infinity? (b) What is the magnification of the lens for that person when their eyes are focused at their near point? Answer: (a) 2.5 (b) 3.5 Diff: 2 Var: 1 Page Ref: Sec ) A person with normal eyesight uses a converging lens of focal length 10 cm. He holds the lens close to his eyes to finish an engraving job. (a) What is the magnifying power of the lens? (b) At what distance from the job he must hold the lens? Answer: (a) 3.5 (b) 7.1 cm Diff: 2 Var: 1 Page Ref: Sec

11 5) You have available lenses of focal lengths 2.0 cm, 4.0 cm, 8.0 cm, and 16.0 cm. (a) If you were to use any two of these lenses to build a telescope, what is the maximum magnification you could achieve? (b) If you were to use any two of these lenses to build a telescope, what is the lens separation for the maximum magnification telescope? Answer: (a) 8.0 (b) 18.0 cm Diff: 1 Var: 1 Page Ref: Sec ) The focal lengths of the objective and the eyepiece of a microscope are 0.5 cm and 2.0 cm, respectively, and their separation adjusted for minimum eyestrain is 6.0 cm. The near-point distance of the person using the microscope is 25.0 cm. (a) If the microscope is focused on a small object, what is the distance between the object and the objective lens? (b) If the microscope is focused on a small object, what is its final magnification? Answer: (a) 0.6 cm (b) -100 Diff: 2 Var: 1 Page Ref: Sec ) The distance between the object and the eyepiece of a compound microscope is 25.0 cm. The focal length of its objective lens is cm and the eyepiece has a focal length of 2.60 cm. A person with a near point 25 cm is using the microscope. (a) What is the largest angular magnification obtainable using the eyepiece alone as a magnifying lens? (b) What is the total magnification of the microscope when used by the person of normal eyesight? Answer: (a) 10.6 (b) Diff: 2 Var: 1 Page Ref: Sec ) A lens of focal length 20 cm has an object of height 3.0 cm placed 100 cm in front of it. The image distance in this case is A) 33 cm. B) 20 cm. C) 25 cm. D) 17 cm. E) -25 cm. 9) An object is placed 40 cm in front of a 20 cm focal length converging lens. How far is the image of this object from the lens? A) 40 cm B) 80 cm C) 20 cm D) 13 cm E) none of the given answers 11

12 10) An object is 12 cm in front of a converging lens with focal length 4 cm. Where is the image? A) 8.0 cm in front the lens B) 8.0 cm behind the lens C) 6.0 cm in front of the lens D) 6.0 cm behind the lens E) 4.0 cm in front of the lens 11) An image is 4.0 mm in front of a converging lens with focal length 5.0 mm. Where is the object? A) 2.2 mm in front of the lens B) 2.2 mm behind the lens C) 9.0 mm in front of the lens D) 9.0 cm behind the lens E) 20 mm in front of the lens 12) A thin converging lens is found to form an image of a distant building 24 cm from the lens. If an object is placed 16 cm from the lens, how far from the object will the image be? A) 64 cm B) 72 cm C) 32 cm D) 96 cm E) 48 cm Diff: 2 Var: 1 Page Ref: Sec ) An object is 80 cm in front of a lens. An image forms 10 cm behind the lens. The lateral magnification A) is -8. B) is C) is 8. D) is E) cannot be determined with the information given. Diff: 1 Var: 1 Page Ref: Sec ) An object is placed 10 cm from a convex lens of focal length 20 cm. What is the magnification? A) 0.50 B) 1.0 C) 1.5 D) 2.0 E) 2.5 Diff: 2 Var: 1 Page Ref: Sec

13 15) An object is placed 60 cm from a convex lens of focal length 10 cm. What is the magnification? A) B) 0.10 C) 0.15 D) 0.20 E) Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 21 cm from a concave lens of focal length 25 cm. What is the magnification? A) B) 0.54 C) D) E) 0.22 Diff: 2 Var: 5 Page Ref: Sec ) It is desired to project an image of an object four times actual size with a lens of focal length 20 cm. What object distance should be used? A) 100 cm B) 80 cm C) 4 cm D) 25 cm E) 5 cm Diff: 2 Var: 1 Page Ref: Sec ) An object, placed 12.0 cm from a lens, produces an image with a magnification of 5.0. What is the focal length of the lens? A) 24 cm B) 18 cm C) 60 cm D) 15 cm E) 9 cm Diff: 2 Var: 1 Page Ref: Sec ) A 4.0 cm tall object is placed 60 cm away from a converging lens of focal length 30 cm. What is the nature and location of the image? A) The image is real, 2.5 cm tall, 30 cm on the same side as object. B) The image is virtual, 2.5 cm tall, 30 cm on the other side of the lens. C) The image is virtual, 2.0 cm tall, 15 cm on the other side of the lens. D) The image is virtual, 4.0 cm tall, 60 cm on the same side as object. E) The image is real, 4.0 cm tall, 60 cm on the other side of the lens. Diff: 2 Var: 5 Page Ref: Sec

14 20) A 4.0-cm-tall object is placed 50.0 cm from a diverging lens of focal length 25.0 cm. What is the nature and location of the image? A) A real image, 4.0 cm tall, 20 cm other side of the object B) A virtual image, 4.0 cm tall, 20 cm other side of the object C) A virtual image, 2.0 cm tall, 10 cm other side of the object D) A virtual image, 1.3 cm tall, 16.7 cm same side as the object E) A real image, 1.3 cm tall, 16.7 cm same side as the object Diff: 2 Var: 5 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 35 cm beyond the first, this second lens having a focal length of 8.0 cm. If the size of the object is 6.0 cm, what is the size of the final image? A) 1.5 cm B) 12 cm C) 9.0 cm D) 3.0 cm E) 6.0 cm Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a diverging lens of focal length -25 cm. A converging lens of focal length cm is placed 30 cm past the first lens. What is the lateral magnification of this system of lenses? A) 2.5 B) -2.5 C) -0.4 D) 1.0 E) 0.4 Diff: 2 Var: 1 Page Ref: Sec ) A lens of focal length 10.0 cm is placed in contact with another lens, the combination having a focal length of 20.0 cm. The focal length of the second lens is A) 200 cm. B) cm. C) cm. D) 10.0 cm. E) 20.0 cm. Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 50 cm. A lens of focal length -20 cm is placed 90 cm beyond the first lens. The final image is located A) 10 cm in front of the second lens. B) 20 cm past the second lens. C) 17 cm past the second lens. D) 10 cm past the second lens. E) 20 cm in front of the second lens. Diff: 2 Var: 1 Page Ref: Sec

15 25) An object is placed 40 cm in front of a lens of focal length 40 cm. A second lens is placed 17 cm beyond the first. An image forms 48 cm past the second lens. The lateral magnification of this system is A) B) C) 1.2. D) 2.8. E) impossible to determine with the information given. Diff: 2 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 35 cm beyond the first, this second lens having a focal length of 8.0 cm. How far past the second lens is the final image formed? A) 40 cm B) 35 cm C) 100 cm D) 6.5 cm E) 25 cm Diff: 3 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a lens of focal length 20 cm. A second lens is placed 15 cm past the first lens. The second lens has a focal length of 40 cm. Where is the final image formed? A) 25 cm in front of the second lens B) 8 cm in front of the second lens C) 8 cm after the second lens D) 10 cm after the second lens E) 25 cm after the second lens Diff: 3 Var: 1 Page Ref: Sec ) An object is placed 100 cm in front of a diverging lens of focal length -25 cm. A converging lens of focal length cm is placed 30 cm past the first lens. Where is the final image formed? A) 30 cm after the second lens B) 20 cm in front of the first lens C) 3 meters before the second lens D) 100 cm after the second lens E) 3 cm before the second lens Diff: 3 Var: 1 Page Ref: Sec ) A lens of focal length 25 cm is placed 50 cm from an object. On the opposite side of the lens at a distance of 50 cm is a plane mirror. Where is the final image formed? A) 50 cm from the lens on the object side B) 35 cm behind the mirror C) 35 cm in front of the mirror D) 50 cm from the lens on the mirror side E) 35 cm from the lens on the object side Diff: 3 Var: 1 Page Ref: Sec

16 30) An object is placed on an optical bench. A lens with a focal length of 12 cm is placed 20 cm from the object. Where should a second lens, with a focal length of 4.0 cm, be placed if a total magnification +6 is to be obtained? A) 20 cm from the first lens B) 35 cm from the first lens C) 40 cm from the first lens D) 30 cm from the first lens E) 25 cm from the first lens Diff: 3 Var: 1 Page Ref: Sec ) An object is placed on an optical bench. A lens with a focal length of 15 cm is placed 30 cm from the object. A diverging lens with a focal length of -10 cm is placed 7.0 cm beyond that. Where is the final image formed, relative to the second lens? A) 45 cm beyond the diverging lens B) 20 cm behind the diverging lens C) 18 cm behind the diverging lens D) 17 cm beyond the diverging lens E) 30 cm beyond the diverging lens Diff: 3 Var: 1 Page Ref: Sec ) A meniscus lens is made with the radius of curvature of the convex surface being 25.0 cm and the concave surface 45.0 cm. If the glass used has index of refraction 1.50, what is the focal length of this lens? A) -32 cm B) 32 cm C) 113 cm D) 67.5 cm E) -113 cm Diff: 2 Var: 1 Page Ref: Sec ) A meniscus lens is made with the radius of curvature of the convex surface being 45.0 cm and the concave surface 25.0 cm. If the glass used has index of refraction 1.50, what is the focal length of this lens? A) 32 cm B) 113 cm C) 25.0 cm D) -32 cm E) -113 cm Diff: 2 Var: 1 Page Ref: Sec ) A doubly convex thin lens is made of glass with an index of refraction of The radii of curvature of the faces of the lens are 60 cm and 72 cm. What is the focal length of the lens? A) 70 cm B) 63 cm C) 75 cm D) 66 cm E) 58 cm Diff: 2 Var: 1 Page Ref: Sec

17 35) A lens is made with focal length -40 cm using a material with index of refraction A second lens is made with the same geometry as the first but using a higher index material, the index being What is the focal length of the second lens? A) -40 cm B) -80 cm C) -53 cm D) -20 cm E) -30 cm Diff: 2 Var: 1 Page Ref: Sec ) A camera lens has a focal length of 50.0 mm and an aperture setting of What is the aperture diameter of this lens? A) 12.5 mm B) 10.1 mm C) 13.6 mm D) 14.2 mm E) 15.0 mm Diff: 1 Var: 1 Page Ref: Sec ) The focal length of a thin lens is 40 mm and its aperture diameter is 10 mm. What is the f-number of this lens? A) 4.0 B) 2.0 C) 5.6 D) 0.30 E) 0.40 Diff: 1 Var: 1 Page Ref: Sec ) The focal length of the lens of a simple camera is 40.0 mm. How far must the lens be moved to change the focus of the camera from a person 25 m away to one that is 4.0 m away? A) 0.2 mm B) 0.3 mm C) 0.4 mm D) 0.5 mm E) 0.7 mm Diff: 2 Var: 1 Page Ref: Sec ) What is the focal length of the corrective contact lens needed by a nearsighted person whose far point is 60 cm? A) -60 cm B) -30 cm C) +30 cm D) +60 cm E) +130 cm Diff: 2 Var: 5 Page Ref: Sec

18 40) A nearsighted person has her distant vision corrected using a -2.0 D lens. Her uncorrected near point is 15 cm. What is her near point using this lens if the lens is 2.0 cm from the eye? A) 17 cm B) 20 cm C) 13 cm D) 18 cm E) 15 cm Diff: 2 Var: 1 Page Ref: Sec ) A nearsighted person has a far point that is 4.2 m from his eyes. What focal length lenses must he use in his contact lenses to allow him to focus on distant objects? A) -4.2 m B) 4.2 m C) -5.2 m D) 5.2 m E) 4.8 m Diff: 2 Var: 1 Page Ref: Sec ) A nearsighted person has a far point that is 4.2 m from his eyes. What focal length lenses in diopters he must use in his contacts to allow him to focus on distant objects? A) 0.48 diopters B) diopters C) diopters D) diopters E) 0.24 diopters Diff: 2 Var: 1 Page Ref: Sec ) What is the focal length of a pair of contact lenses that will allow a person with a near point of cm to read a newspaper held 25.0 cm from his eyes? A) -100 cm B) cm C) 10.2 cm D) 20.8 cm E) 31.3 cm Diff: 2 Var: 1 Page Ref: Sec ) What power contact lens should be used to correct the vision of a farsighted person whose near point is 80 cm to see something clearly at a distance of 25 cm? A) 2.8 diopters B) -2.8 diopters C) -4.0 diopters D) -4.2 diopters E) 4.2 diopters Diff: 2 Var: 1 Page Ref: Sec

19 45) What power contact lens must be used to correct the vision of a nearsighted person whose far point is 40 cm? A) 2.5 diopters B) -2.5 diopters C) -3.6 diopters D) -4.0 diopters E) 4.0 diopters Diff: 2 Var: 1 Page Ref: Sec ) What is the near point of a farsighted person who can read a newspaper held 25 cm from his eyes when he wears 3.33 diopters glasses? A) 1.5 m B) 0.50 m C) 1.9 m D) 0.75 m E) 0.60 m Diff: 2 Var: 1 Page Ref: Sec ) A person can read the newspaper when it is held at 60 cm from his eyes. What should the focal length of his contact lenses be to allow him to read the newspaper comfortably at a distance of 30 cm? A) -30 cm B) +30 cm C) -60 cm D) +60 cm E) +90 cm Diff: 2 Var: 1 Page Ref: Sec ) John is nearsighted and cannot see things beyond 110 cm from his eyes. What is the focal length of the contact lenses that will enable him to see distant objects clearly? A) +50 cm B) -50 cm C) -110 cm D) +110 cm E) -30 cm Diff: 2 Var: 5 Page Ref: Sec ) John is nearsighted and cannot see things beyond 90 cm from his eyes. What is the refractive power of the contact lenses that will enable him to see distant objects clearly? A) +1.1 diopters B) -1.1 diopters C) -1.7 diopters D) -2.2 diopters E) +2.2 diopters Diff: 2 Var: 5 Page Ref: Sec

20 50) Jill is farsighted and cannot see objects clearly that are closer to the eye than 80.0 cm. What is the focal length of the contact lenses that will enable her to see objects at a distance of 25.0 cm from her eyes? A) cm B) cm C) cm D) cm E) cm Diff: 2 Var: 5 Page Ref: Sec ) Jill is farsighted and cannot see objects clearly that are closer to the eye than 80.0 cm. What is the refractive power of the contact lenses that will enable her to see objects at a distance of 25.0 cm from her eyes? A) diopters B) diopters C) diopters D) diopters E) diopters Diff: 2 Var: 5 Page Ref: Sec ) A nearsighted person cannot see objects beyond 80 cm from his eyes. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable him to see the distant objects clearly? A) +80 cm, +1.3 diopters B) -80 cm, +1.3 diopters C) +80 cm, -1.3 diopters D) -80 cm, -1.3 diopters E) -1.3 cm, +1.3 diopters Diff: 2 Var: 5 Page Ref: Sec ) A far sighted person can not see clearly objects that are closer to his eyes than 60.0 cm. Which one of the following combinations represents the correct focal length and the refractive power of the contact lenses that will enable him to see the objects at a distance of 25.0 cm from his eyes? A) cm, diopters B) cm, diopters C) cm, diopters D) cm, diopters E) +60 cm, diopters Diff: 2 Var: 5 Page Ref: Sec ) A magnifying glass produces an angular magnification of 7. What is the focal length of this lens if a person whose near point is 28 cm reads a book using this magnifying glass? A) 2 cm B) 3 cm C) 4 cm D) 5 cm E) 6 cm Diff: 1 Var: 1 Page Ref: Sec

21 55) The focal length of a magnifying glass is 15 cm. If the near point of a person is 25 cm, what is the magnification of this glass for this person when his eyes are focused at infinity? A) 1.7 B) 2.7 C) 3.7 D) 4.7 E) 5.7 Diff: 1 Var: 1 Page Ref: Sec ) What is the magnification of a magnifying glass of focal length 4.0 cm if the image is to be viewed by a relaxed eye with a near point of 25 cm? A) 2.0 B) 3.0 C) 3.6 D) 4.0 E) 6.3 Diff: 1 Var: 1 Page Ref: Sec ) A magnifying glass uses a converging lens with a refractive power of 20 diopters. What is the magnification if the image is to be viewed by a relaxed eye with a near point of 25 cm? A) 5.0 B) 3.0 C) 4.0 D) 1.0 E) 2.0 Diff: 2 Var: 1 Page Ref: Sec ) What is the maximum possible magnification of the converging lens of focal length 5 cm? A) 2 B) 3 C) 4 D) 5 E) 6 Diff: 2 Var: 1 Page Ref: Sec ) The objective lens of a refracting telescope has a focal length of 60 cm and the eyepiece a focal length of 8.0 cm. What is the angular magnification of the telescope? A) 34 B) 480 C) 68 D) 0 E) 7.5 Diff: 1 Var: 1 Page Ref: Sec

22 60) An astronomical telescope has an objective of diameter 20 cm with a focal length of 180 cm. The telescope is used with an eyepiece of focal length 3.0 cm. The magnifying power of the telescope is A) 360 X. B) 60 X. C) 540 X. D) 7 X. E) 180 X. Diff: 1 Var: 1 Page Ref: Sec ) The focal length of the objective of a telescope is 75.0 cm. While the eyepiece has a focal length of 6.00 cm, what is the magnifying power of this telescope? A) B) C) 450 D) 12.5 E) 200 Diff: 1 Var: 1 Page Ref: Sec ) The length of a telescope is 2.00 m and the focal length of the objective is 2.0 cm. What is the focal length of the eyepiece? A) 200 cm B) 202 cm C) 101 cm D) 2.0 cm E) 198 cm Diff: 1 Var: 1 Page Ref: Sec ) The length of a telescope is 2.20 m and the focal length of the eyepiece is 1.9 cm. What is the focal length of the objective? A) 41 cm B) 45 cm C) 111 cm D) 218 cm E) 16 cm Diff: 1 Var: 1 Page Ref: Sec ) The focal length of the objective of a telescope is 0.2 m and the eyepiece has a focal length of 1.6 m. What is the length of this telescope? A) 8.0 m B) 1.4 m C) 0.90 m D) 1.6 m E) 1.8 m Diff: 2 Var: 1 Page Ref: Sec

23 65) A student constructs an astronomical telescope with a magnification of 10. If the telescope has a converging lens of focal length 50 cm, what is the resulting length of the telescope? A) 53 cm B) 55 cm C) 60 cm D) 67 cm E) 75 cm Diff: 2 Var: 1 Page Ref: Sec ) The length of the telescope is 1.60 m and it has a magnification of What is the focal length of the objective? A) 60.0 cm B) 157 cm C) 100 cm D) 128 cm E) 96.0 cm Diff: 2 Var: 1 Page Ref: Sec ) The length of a telescope is 1.60 m and it has a magnification of What is the focal length of the eyepiece? A) 2.62 cm B) 60.0 cm C) 100 cm D) 1.16 cm E) 96.0 cm Diff: 2 Var: 1 Page Ref: Sec ) The focal lengths of the objective and eyepiece in a compound microscope are 0.8 cm and 2.5 cm, respectively. The image formed by the objective is 16 cm from it and the final image is 25 cm from the eye. What is the total magnification? A) B) C) -2.0 D) -100 E) -200 Diff: 2 Var: 1 Page Ref: Sec ) The focal lengths of the objective and eyepiece in a compound microscope are 0.50 cm and 2.00 cm, respectively. An object is placed at a distance of 0.52 cm from the objective. If the final image seen by the eye is at a distance of 25 cm from it, what is the magnification? A) -125 B) -100 C) -225 D) -325 E) -425 Diff: 2 Var: 1 Page Ref: Sec

24 70) The focal lengths of the objective and the eyepiece in a microscope are 0.29 cm and 2.50 cm, respectively. An object is placed at 0.30 cm from the objective lens and the image of this object is viewed with the eyepiece adjusted for minimum eyestrain. The near-point distance of the person using the microscope is 25.0 cm. What is the final magnification of the microscope? A) -190 B) -240 C) -300 D) -310 E) -470 Diff: 2 Var: 1 Page Ref: Sec ) The distance between the object and the eyepiece of a compound microscope is 18.0 cm. The focal length of its objective lens is 0.80 cm and the eyepiece has a focal length of 2.3 cm. The near-point distance of the person using the microscope is 25.0 cm. What is the total magnification of the microscope? A) -120 B) -184 C) -200 D) -360 E) -480 Diff: 2 Var: 1 Page Ref: Sec ) A microscope has an objective lens of focal length 1.4 mm and an eyepiece of focal length 20 mm, adjusted for minimum eyestrain. A blood sample is placed 1.5 mm from the objective. How far apart are the lenses? A) 20 mm B) 21 mm C) 23 mm D) 33 mm E) 41 mm Diff: 2 Var: 1 Page Ref: Sec ) The focal lengths of the objective and the eyepiece in a microscope are 0.29 cm and 2.5 cm, respectively. An object is placed 0.3 cm from the objective. The image of this object is viewed with the eyepiece adjusted for minimum eyestrain. What is the distance between the objective and the eyepiece? A) 9.85 cm B) 10.1 cm C) 10.4 cm D) 11.2 cm E) 11.5 cm Diff: 2 Var: 1 Page Ref: Sec