Exam 4. P202 Spring 2004 Instructor: Prof. Sinova

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1 Exam 4 P202 Spring 2004 Instructor: Prof. Sinova Name: Date: 4/22/04 Section: All work must be shown to get credit for the answer marked. You must show or state your reasoning. If the answer marked does not obviously follow from the shown work, even if the answer is correct, you will not get credit for the answer. (5)1. Which one of the following statements best explains why interference patterns are not usually observed for light from two ordinary light bulbs? A) Diffraction effects predominate. B) The two sources are out of phase. C) The two sources are not coherent. D) The interference pattern is too small to observe. E) Light from ordinary light bulbs is not polarized. (5)2. Light of wavelength 530 nm is incident on two slits that are spaced 1.0 mm apart. How far from the slits should the screen be placed so that the distance between the m = 0 and m = 1 bright fringes is 1.0 cm? A) 7.9 m B) 9.5 m C) 16 m D) 19 m E) 36 m (5)3. 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 nm in air? A) 89 nm B) 125 nm C) 170 nm D) 250 nm E) 357 nm Page 1

2 (5)4. Light of nm is incident on a single slit of width 6.5 µm. The resulting diffraction pattern is observed on a nearby screen and has a central maximum of width 3.5 m. What is the distance between the screen and the slit? A) 9.5 m B) 19 m C) 38 m D) 57 m E) 76 m (8)5. A spy satellite is in orbit at a distance of 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. (5)6. Light from a laser (λ = 640 nm) passes through a diffraction grating and spreads out into three beams as shown in the figure. Determine the spacing between the slits of the grating. A) 240 nm B) 410 nm C) 500 nm D) 680 nm E) 800 nm Page 2

3 (5)7. Which one of the following statements provides the most convincing evidence that electromagnetic waves have a transverse character? A) Electromagnetic waves can be refracted. B) Electromagnetic waves can be reflected. C) Electromagnetic waves can be polarized. D) Electromagnetic waves can be diffracted. E) Electromagnetic waves exhibit interference. (5)8. Light is usually thought of as wave-like in nature and electrons as particle-like. In which one of the following activities does light behave as a particle or does an electron behave as a wave? A) A Young's double slit experiment is conducted using blue light. B) X-rays are used to examine the crystal structure of sodium chloride. C) Water is heated to its boiling point in a microwave oven. D) An electron enters a parallel plate capacitor and is deflected downward. E) A beam of electrons is diffracted as it passes through a narrow slit. (5)9. A laser emits a pulse of light with energy J. Determine the number of photons in the pulse if the wavelength of light is 480 nm. A) B) C) D) E) (5)10. Photons of energy 6 ev cause electrons to be emitted from a certain metal with a maximum kinetic energy of 2 ev. If photons of twice the wavelength are incident on this metal which one of the following statements is true? A) No electrons will be emitted. B) Electrons will be emitted with a maximum kinetic energy of 1 ev. C) Electrons will be emitted with a maximum kinetic energy of 8 ev. D) Electrons will be emitted with a maximum kinetic energy of 10 ev. E) Electrons will be emitted with a maximum kinetic energy of 20 ev. Page 3

4 (5)11. A photon of wavelength 200 nm is scattered by an electron that is initially at rest. Which one of the following statements concerning the wavelength of the scattered photon is true? A) The wavelength is zero nm. B) The wavelength is 200 nm. C) The wavelength is 100 nm. D) The wavelength is greater than 200 nm. E) The wavelength is less than 200 nm, but greater than zero. (5)12. Determine the de Broglie wavelength of a neutron (m = kg) that has a speed of 5.0 m/s. A) 79 nm B) 162 nm C) 395 nm D) 529 nm E) 1975 nm (7)13. The speed of a bullet with a mass of kg is 420 m/s with an uncertainty of %. What is the minimum uncertainty in the bullet's position if it is measured at the same time as the speed is measured? A) m B) m C) m D) m E) m (5)14. Which model of atomic structure was developed to explain the results of the experiment shown? A) Bohr model B) nuclear atom C) billiard ball atom D) plum-pudding model E) quantum mechanical atom Page 4

5 (5)15. Which one of the following statements is the assumption that Niels Bohr made about the angular momentum of the electron in the hydrogen atom? A) The angular momentum of the electron is zero. B) The angular momentum can assume only certain discrete values. C) Angular momentum is not quantized. D) The angular momentum can assume any value greater than zero because it's proportional to the radius of the orbit. E) The angular momentum is independent of the mass of the electron. (5)16. Which one of the following sets of quantum numbers is not possible? n m m s A) /2 B) /2 C) /2 D) /2 E) /2 (5)17. Calculate the K α X-ray wavelength for a gold atom (Z = 79). A) m B) m C) m D) m E) m (5)18. Name the physicist credited with the following statement: No two electrons in an atom can have the same set of values for the four quantum numbers. A) Werner Heisenberg B) Wolfgang Pauli C) Arthur Compton D) Niels Bohr E) Erwin Schrödinger (5)19. Complete the following sentence: In the condition known as population inversion, A) the amount of one type of gas atoms is larger than that of another in a mixture. B) the number of energy levels that are populated is larger than that of unpopulated levels. C) there are more electrons occupying lower energy levels than occupying higher energy levels. D) there are more electrons occupying higher energy levels than occupying lower energy levels. E) there are more photons than electrons in a given system. Page 5

6 Answer Key 1. C 2. D 3. A 4. B 5. E 6. E 7. C 8. E 9. C 10. A 11. D 12. A 13. B 14. B 15. B 16. A 17. C 18. B 19. D Page 6

A) n L < 1.0 B) n L > 1.1 C) n L > 1.3 D) n L < 1.1 E) n L < 1.3

A) n L < 1.0 B) n L > 1.1 C) n L > 1.3 D) n L < 1.1 E) n L < 1.3 1. A beam of light passes from air into water. Which is necessarily true? A) The frequency is unchanged and the wavelength increases. B) The frequency is unchanged and the wavelength decreases. C) The