Exam 3 - Winter 2008

University of Michigan Name___________________ Physics 126 Winter 2008 Section_______ Sample Exam 3 Instructions: You may use a new notecard on two sides of a 3x5 index card, plus your notecards from Exam 1 and Exam 2 The time for the exam is 90 minutes + maybe bonus time The real exam will have 20 questions. Useful Physical Constants: Discussion Sections 19 12 2 2 0 922 0 1.602 10 C 8.85 10 C /(N m ) 1/(4 ) 8.99 10 N m /C e k ? ?? ? ? =× =× ? ==×? 4 7 0 8 -34 -31 e -27 2 -19 p 1 G 10 1 eV 1.6 410 Tm/A c = 2.997 10 m/s h = 6.626 10 J-s m = 9.11 10 kg m = 1.67 10 kg g = 9.8 m/s T 10 J ? ? ? ? = = =× ? × × × × × # time leader 3 8 am Bobkov 4 9 am Bobkov 5 10 am Bobkov 6 8 am Moukouri 7 9 am Moukouri 8 10 am Moukouri 12 11 am Bobkov 13 12 noon Qian 15 1 pm Qian 16 2 pm Qian 17 3pm Cohen Page 2 1. A concave mirror in an amusement park has a radius of curvature of 4.0 m. A child stands in front of the mirror so that she appears 2.5 times taller than her actual height. If the image is upright, how far is she standing from the mirror? A) 1.2 m B) 3.5 m C) 2.8 m D) 4.0 m E) 7.0 m 2. The rectangular metal tank shown is filled with an unknown liquid. The observer, whose eye is level with the top of the tank, can just see corner E. The index of refraction of this liquid is: A) 1.75 B) 1.67 C) 1.50 D) 1.33 E) 1.25 Use the following to answer question 3: Light in air is incident on a plastic plate at the Brewster angle. The angle of refraction is 35.0°. 3. What is the index of refraction of the plastic plate? A) 1.58 B) 1.36 C) 1.43 D) 1.61 E) 1.74 4. A transparent film (n = 1.4) is deposited on a glass lens (n = 1.5) to form a non- reflective coating. What thickness would prevent reflection of light with wavelength 5.00 × 10 2 nm in air? A) 89 nm B) 125 nm C) 170 nm D) 250 nm E) 357 nm Page 3 5. A pulsed laser has an average output power of 4.0 W. Each pulse consists of light at wavelength 5.0 × 10 ?7 m and has a 25 ms duration. How many photons are emitted in a single pulse? A) 1.0 × 10 17 B) 2.5 × 10 17 C) 3.7 × 10 17 D) 5.0 × 10 17 E) 7.4 × 10 17 6. A child sitting at the edge of a swimming pool sees a coin resting on the bottom of the pool. The coin appears to be 2.0 ft directly below the water's surface. How deep is the pool at the location of the coin? The index of refraction of water is 1.33. A) 1.5 ft B) 2.0 ft C) 2.7 ft D) 3.2 ft E) 4.0 ft 7. A beam of electrons is incident on a single slit that has a width of 1.00 × 10 ?6 m and a diffraction pattern is observed on a screen located 15.0 m from the slit. The momentum of an individual electron in the beam is 5.91 × 10 ?24 kg ? m/s. What is the width of the central maximum fringe? A) 5.87 × 10 ?5 m B) 1.33 × 10 ?4 m C) 6.67 × 10 ?4 m D) 3.37 × 10 ?3 m E) 7.50 × 10 ?3 m 8. Joseph uses a converging lens (f = 0.12 m) to read a map located 0.080 m from the lens. What is the magnification of the lens? A) +3.4 B) +3.0 C) +1.7 D) +0.60 E) +0.33 9. A convex mirror has a radius of curvature of 0.50 m. Where must an object be placed in front of the mirror such that the image is formed 0.15 m behind the mirror? A) 0.38 m B) 0.19 m C) 0.77 m D) 0.093 m E) 0.57 m Page 4 Use the following to answer questions 10-11: A 1.5-cm tall object is placed 0.50 m to the left of a diverging lens with a focal length of 0.20 m. A converging lens with a focal length of 0.17 m is located 0.08 m to the right of the diverging lens. 10. What is the height and orientation with respect to the original object of the final image? A) 1.4 cm, inverted B) 1.4 cm, upright C) 0.95 cm, inverted D) 0.95 cm, upright E) 0.28 cm, inverted 11. What is the location of the final image with respect to the object? A) The final image is located 0.14 m to the left of the object. B) The final image is located 0.32 m to the right of the object. C) The final image is located 0.40 m to the right of the object. D) The final image is located 0.83 m to the right of the object. E) The final image is located 1.3 m to the right of the object. 12. A monochromatic beam of microwaves with a wavelength of 0.052 m is directed at a rectangular opening of width 0.35 m. The resulting diffraction pattern is measured along a wall 8.0 m from the opening. What is the distance between the first- and second-order dark fringes? A) 1.3 m B) 1.8 m C) 2.1 m D) 2.5 m E) 3.7 m 13. Light with a wavelength of 589 nm in a vacuum strikes the surface of an unknown liquid at an angle of 31.2° with respect to the normal to the surface. If the light travels at a speed of 1.97 × 10 8 m/s through the liquid, what is the angle of refraction? A) 19.9° B) 26.1° C) 34.2° D) 39.3° E) 51.9° Page 5 Use the following to answer question 14: A beam of light that consists of a mixture of red, green and violet light strikes a prism (surrounded by air) as shown. Indices of refraction for this prism for the various colors are indicated in the table. An observer is located to the right of the prism as shown. 14. Which color(s) could, in principle, be seen by the observer? A) only red light B) only green light C) only violet light D) only green and red light E) only green and violet light 15. You set two parallel slits 0.1 mm apart at a distance of 2 m from a screen and illuminate them with light of wavelength 450 nm. The distance between a bright spot in the interference pattern and the dark spot adjacent to it is A) 0.560 mm B) 1.12 mm C) 2.25 mm D) 4.50 mm E) 9.00 mm 16. Photons of what minimum frequency are required to remove electrons from gold? Note: The work function for gold is 4.8 eV. A) 7.3 × 10 14 Hz B) 1.2 × 10 15 Hz C) 3.8 × 10 17 Hz D) 6.5 × 10 15 Hz E) 4.6 × 10 14 Hz Page 6 17. The right lens of Josh's contact lenses is a converging lens of +2.50 diopters. He can read a book held as close as 25 cm from his eyes. Without his lenses, Josh's right eye has A) a far point of 15.4 cm. B) a far point of 40.0 cm. C) a far point of 66.7 cm. D) a near point of 15.4 cm. E) a near point of 66.7 cm. 18. Calculate the K ? X-ray wavelength for a gold atom (Z = 79). A) 5.13 × 10 ?10 m B) 8.54 × 10 ?10 m C) 2.00 × 10 ?11 m D) 3.60 × 10 ?11 m E) 2.47 × 10 ?13 m 19. An electron is in the ground state of a hydrogen atom. A photon is absorbed by the atom and the electron is excited to the n = 2 state. What is the energy in eV of the photon? A) 13.6 eV B) 10.2 eV C) 3.40 eV D) 1.51 eV E) 0.54 eV 20. A spy satellite is in orbit at a distance of 1.0 × 10 6 m above the ground. It carries a telescope that can resolve the two rails of a railroad track that are 1.4 m apart using light of wavelength 600 nm. Which one of the following statements best describes the diameter of the lens in the telescope? A) It is less than 0.14 m. B) It is greater than 0.14 m and less than 0.23 m. C) It is greater than 0.23 m and less than 0.35 m. D) It is greater than 0.35 m and less than 0.52 m. E) It is greater than 0.52 m. 21. In a cinema, a picture 2.5 cm wide on the film is projected to an image 3.0 m wide on a screen which is 18 m away. The focal length of the lens is about: A) 7.5 cm B) 10 cm C) 12.5 cm D) 15 cm E) 20 cm Page 7 Answer Key 1. A 2. E 3. C 4. A 5. B 6. C 7. D 8. B 9. A 10. A 11. E 12. A 13. A 14. E 15. D 16. B 17. E 18. C 19. B 20. E 21. D amidei Microsoft Word - sample_exam_3.doc