The hardest MC questions in optics. A guide for the perplexed

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1 The hardest MC questions in optics. A guide for the perplexed

2 PHYSICS 123 Exam 3 Spring 2011 Instr: David D. Allred CID# The first part of the exam is multiple choice. Choose the best answer. After that comes several homework-style problems which will be graded by hand. Instructions: Partial credit will be given so please answer these problems clearly and label your work carefully. Always calculate to at least 4 decimal places. Also see that your answers and scratch work are attached to your test as you leave the testing center. Make sure to put your work in order. Staple it to the cover sheet well. It is a good idea to write your I.D. number on each sheet. You may call me at or office , home SI units and right-handed coordinate systems are to be assumed unless otherwise indicated. You can use: a calculator of any kind, scratch paper, the chapter summaries No time limit. Good luck! I will have question(s) from exam later. Start This evening. Friday is Late day to 5 p.m.

3 Review: Compare Mirrors q + = M = p q f p Which is true? A. p >0, q>0 B. p >0, q<0 C. p <0, q>0 D. p <0, q<0

4 # An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. Is the mirror A. Concave? B. Convex Outer

5 # An object is 12.0 cm from the Outer curved surface of a hemispherical bowl that is 8.00 cm in radius. Is the image A. inverted? B. upright?

9 # An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. Is the image A. Smaller B. Larger? C. Same size as the object

10 # (~ 27%) An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. What is the magnitude of the focal length of the bowl? D 27% LMD A. 1 B. 2 C. 3-4 D. 5-6 E. 7-9

11 # An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. What is the sign of the focal length of the bowl? D 27% LMD A. + B. - C. Zero

12 # An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. What is the sign of the q for the image? D 27% LMD A. + B. - C. Zero How do you know?

13 # (~ 27%) An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. What is the magnitude of the magnification of the image? D 27% LMD A. 1 B. 2 C. 3-4 D. 5-6 E. 7-9

14 # An object is 12.0 cm from the curved surface of a hemispherical bowl that is 8.00 cm in radius. What is the sign of the magnification of the image? D 27% LMD A. + B. - C. Zero

15 #7 exam 3 (~33%) 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 33% a. upright, diminished and virtual b. inverted, diminished and real c. upright, enlarged and virtual d. inverted, enlarged and real

16 #5 exam 3 (~45%) B 45% 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 magnitude of the magnification less than one b. real, inverted & magnitude of the magnification greater than one c. virtual, upright and magnitude of the magnification greater than one d. real, inverted and magnitude of the magnification less than one

17 Projector f=10cm Q=4m Distance between projector and screen =4m q=4m f=10cm = = + p = 10.26cm f p q = + =

18 Consider a projector and a screen 1 m apart. The image is in focus on the screen. If we move the screen closer to the projector, which way should we move the lens on the projector in order to bring the image into focus on the screen again? A. Move the lens towards the screen B. Move the lens away from the screen Is that what we observed?

19 Exam T/F I have seen the dollar bill illusion in the ESC and understand how it works basically. A True; B False An extra credit question based on energy lecture. 20 MC 2 HW style 4 pages 2½ hrs.

20 #15 exam 3 (54%) B 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 a virtual image from the objective as the object and forms its own real image. d. uses a virtual image from the objective as the object and forms its own virtual image.

21 Fig. 25-7a, p.827

22 Fig. 25-6b, p.826

23 Are the small images of the space needle in the rain drops virtual or real? You are looking through a windshield at the space needle. A. Real B virtual C. insufficient info

24 43. Exam 3 (~ 21%) (EXTRA credit) D Two thin lenses, with focal lengths of 25.0 cm and cm are placed in contact in an orientation so that their optic axes coincide. What is the focal length of the two in combination? Hint: A thin lens is one whose thickness is negligible. 21% a cm b cm c cm d. 150 cm

Geometric Optics Practice Problems. Ray Tracing - Draw at least two principle rays and show the image created by the lens or mirror.

Geometric Optics Practice Problems Ray Tracing - Draw at least two principle rays and show the image created by the lens or mirror. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Practice Problems - Mirrors Classwork