ASTRONOMY 111 Session 003 Fall 2007 Date: Oct. 29, 2007 Instructor: Dr. Jie Zhang In-class Exam #2 I understand that this examination lasts from 7:20 PM to 8:20 PM. I have not received, nor given any aid, nor assistance, nor answers, nor questions to anyone else during this examination period. I understand that any violation of the GMU honor code will result in my being reported directly to the honor committee, without warning. I understand that any honor code violation can cause me to fail the course, be suspended, and/or be expelled from the university; and, it will automatically be entered into my official records. Test Form: X Name (Print): _____________________ Signature: _____________________ Student ID: _____________________ In your scantron, please record the ID number (from far-left to right, the 8-digit G number without letter G), name, subject and date. The class will resume at 8:30 PM. Please come back at this time. Chap. 0: 1 Chap. 5: 12 Chap. 6: 8 Chap. 7: 10 Chap. 8: 8 Chap. 9: 11 Note: Answer Keys --- asterisk symbol indicate the correct answer(Chap. 0) 1. Your answer to question 1 must be “A” (Chap. 5) 2. The speed of light in the vacuum is A 3.0×104 km/s B *3.0×105 km/s C 3.0×106 km/s D 3.0×107 km/s 3. Which one of the following statements is true? A *Visible light takes up only a very small part of the total range of wavelengths in the electromagnetic spectrum. B Visible light takes up most (but not all) of the total range of wavelengths in the electromagnetic spectrum. C Visible light takes up all of the electromagnetic spectrum. D Visible light is not part of the electromagnetic spectrum. 4. Which of the following groups have electromagnetic wavelengths, all of which are longer than visible light: A ultraviolet, microwave, radio B ultraviolet, x-ray, gamma ray C *infrared, microwave, radio D none of the above has wavelengths with all greater than visible light 5. The Kelvin scale measures A temperature referenced to zero at the freezing point of water. B mass per unit volume, or density, with water having a value of 1.0. C temperature in Fahrenheit-sized degrees above absolute zero. D *temperature in Celsius-sized degrees above absolute zero. 6. A perfect blackbody is so named because it A reflects only the radiation falling on it and emits none of its own. B *absorbs all radiation falling on it and reflects none. C never emits radiation. D always emits the same amount and color of radiation regardless of its temperature. 7. According to the Wien’s Law of blackbody A the wavelength of light is shifted to a shorter wavelength if the source of light is moving toward you. B the wavelength of light is shifted to a longer wavelength if the source of the light is moving toward you. C the wavelength of peak emission of light from a blackbody is shifted to a longer wavelength when the temperature of the blackbody increases D *the wavelength of peak emission of light from a blackbody is shifted to a shorter wavelength when the temperature of the blackbody increases8. Blackbody “A” is at 6000 degrees K while blackbody “B” is at 3000 degrees K. Therefore blackbody “A” gives off _____times more total energy than blackbody “B” (Using Stefen-Boltzman Law: F = σT4) A *16 B 8 C 4 D 2 9. The spectrum of a pure blackbody is A *a continuous spectrum B an absorption spectrum C an emission spectrum D any of the above 10. The physical structure of an atom is A neutrons orbiting an electrically neutral nucleus of protons and electrons. B *negatively charged electrons moving around a very small but massive, positively charged nucleus. C positively and negatively charged particles orbiting a small but powerful black hole. D negatively charged electrons and positively charged protons mixed uniformly in the volume of the atom. 11. What happens when an electron in a hydrogen atom in the n=3 energy level jumps to the n=2 energy level A It absorbs a photon B *It emits a photon C It is ionized to become a free electron D It collides with the proton. 12. Electrons in atoms A *occupy discrete orbits whose energies are fixed. B can have any energy. C cannot interact with light. D can only absorb light. 13. According to the Doppler effect, A *the wavelength of light is shifted to a shorter wavelength if the source of light is moving toward you. B the wavelength of light is shifted to a longer wavelength if the source of the light is moving toward you. C the wavelength of peak emission of light from a source changes as the temperature of the source changes. D spectral lines are split into two or more wavelengths when the source of the light is in a strong magnetic field.(chap 6) 14. What is the refraction of light? A the change in direction of a light ray as it reflects from a more dense material than the one in which it is traveling B the absorption of light as it traverses a dense, transparent material C the breaking of white light into its composite colors D *the change in direction of a light ray as it crosses from a less dense, transparent material to a more dense one 15. Which type of telescope uses a lens as the main optical element? A radio telescope B all telescopes C reflecting telescope D *refracting telescope 16. Which of the following aspects of a telescope is most important? A High magnification B *Large light-gathering power C Long focal length D Secondary mirror configuration 17. The limit to how sharply we can resolve stars from a ground-based telescope, but not a space-based telescope, is A the diameter of the primary mirror or objective lens. B the light-gathering power. C *the stability of the atmosphere. D the pixel sizes of CCD camera 18. The limit to how sharply we can resolve stars from a space-based telescope, but not a ground-based telescope, is A *the diameter of the primary mirror or objective lens. B the light-gathering power. C the stability of the atmosphere. D the quality of the camera optics. 19. A spectrograph is usually used in astronomy to measure the A variation of the mass of an object as it moves through space. B *distribution of light intensity among the various wavelengths C vibration of Earth following an earthquake. D the distance of a remote star 20. The two ranges of electromagnetic radiation for which Earth's atmosphere is reasonably