Last updated: November 12, 2008
PHY 2054 Discussion – Fall ‘08
Practice Exam Problems (Chapter 23)
1.
The lateral magnification for a flat mirror: (Properties of Flat Mirrors) a. is a function of the object distance. B. is a function of the image distance c. is a function of the object and image distance d. is 1
2.
How large should a wall-mounted mirror be to view the upper half of ones height, h ? (Required
Length of Flat mirrors) a. h b. h /2 c. h /4 d. The answer is not given.
3.
A girl standing in front of a concave mirror. Consider two rays of light, one from her nose and one from her mouth that are parallel to the principal axis as they are traveling toward the mirror. These rays will come together: (Ray Diagram) 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.
4.
A candle is 49.0 cm in front of a convex spherical mirror of radius of curvature 70.0 cm. What are the image distance and the magnification, respectively? (Convex Mirror) a. -20.4 cm, +0.417 b.
+20.4 cm, -0.417 c. +122.5 cm, +2.50 d. -20.4 cm, -0.417
5.
An object is placed 12 cm from a concave mirror produces a real image 8.0 cm from the mirror. If the object is now moved to a new position 18.0 cm from the mirror, where is the new image located as measured from the mirror? (Concave Mirror) a. 3.0 cm b. 6.5 cm c. 92 cm d. 14.6 cm
6.
A solid glass sphere with a radius of 5.00 cm and index of refraction of 1.52 has a small coin embedded 3.00 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? (Image due to Spherical Lenses) a. 2.48 cm b. 3.20 cm c. 5.00 cm d. 6.85 cm
7.
A container is filled with fluid 1 and the apparent depth of the fluid is 5.00 cm. The container is next filled with fluid 2 and the apparent depth of this fluid is 4.00 cm. If the index of refraction of the first fluid is 1.60, what is the index of refraction of the second fluid? (Apparent Depth & Refractive
Index) a. 2.00 b. 1.79 c. 1.28 d. More information is needed to find the value.
8.
If atmospheric refraction did not occur, how would the apparent time of sunrise and sunset be changed? (Atmospheric Refraction) 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
9.
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? (Lens
Maker’s Equation) a. -20 cm b. +6.7 cm c. +10 cm d. +20 cm
10.
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? (Converging Lens) a. inverted, enlarged and real b. upright, enlarged and virtual c. upright, diminished and virtual d. inverted, diminished and real
11.
An object, located 90 cm from a concave lens, forms an image 60 cm from the lens on the same side as the object. What is the focal length of the lens? (Diverging Lens) a. -36 cm b. -75 cm c. -180 cm d. -150 cm
12.
Three thin lenses, each of focal length f , are placed in contact. What is the resulting focal length of the combination? (Thin Lenses in Contact) a. f b. 3 f c. f /3 d. 3/ f
13.
Two convex thin lenses with focal lengths 10.0 cm and 20.0 cm are aligned on a common axis, running left to right, the 10-cm lens being on the left. A distance of 20.0 cm separates the lenses. An object is located at a distance of 15.0 cm to the left of the 10-cm lens. Where will the final image appear as measured from the 20-cm lens? (Combination of Lenses) a. -13.3 cm b. -6.67 cm c.
+6.67 cm d. +13.3 cm
14.
An object is placed 25 cm to the left of a lens of focal length 20 cm. 75 cm to the right of this lens is a plane mirror. Where does the final image form? (Combination of Mirrors & Lenses) a. 25 cm to the right of the mirror. b. 25 cm to the left of the mirror c. 50 cm to the left of the lens d. 100 cm to the left of the lens
Answers: 1-d 2-c 3-a 4-a 5-b 6-a 7-a 8-c 9-d 10-b 11-c 12-c 13-c 14-c