Phys 100 Astronomy (Dr. Ilias Fernini) Review Questions for Chapter 5 MULTIPLE CHOICE 1. What is the wavelength of the longest wavelength light visible to the human eye? a. 400 nm b. 4000 nm c. 7000 nm * d. 700 nm e. 3 10 8 m 2. What is the wavelength of the shortest wavelength light visible to the human eye? * a. 400 nm b. 4000 nm c. 7000 nm d. 700 nm e. 3 10 8 m 3. Violet light has a wavelength of approximately. * a. 400 nm b. 4000 nm c. 7000 nm d. 700 nm e. 3 10 8 m 4. has (have) wavelengths that are longer than visible light. a. Gamma-rays b. Ultraviolet light * c. Infrared radiation d. X-rays e. a, b and d above 5. There are nanometers in one meter. a. 1 10 3 b. 1 10-3 c. 1 10 9 * d. 1 10-9 e. 400 6. has (have) wavelengths that are shorter than visible light. a. Gamma-rays b. Ultraviolet light c. Infrared radiation d. Radio 1
* e. a and b 7. Astronomers build optical telescopes on tops of mountains because a. there is less air to dim the light. b. the seeing is better. c. CCDs work better when there is less oxygen in the air. d. all of the above * e. a and b 8. Ultraviolet radiation from a star * a. will not penetrate Earth's atmosphere and reach the ground. b. has a wavelength that is longer than the visible light emitted by the star. c. has a wavelength that is shorter than the x-rays emitted by the star. d. a and b e. b and c 9. A new generation of telescopes is currently being built that overcomes the limitations of the older large telescopes. Some of these new telescopes a. use segmented mirrors. b. use mirrors that are very thin. c. use active optics to control the shape of the mirror. * d. all of the above 10. The ability of a telescope to resolve fine detail is known as the telescope s. a. light gathering power b. focal length * c. resolving power d. telescope detailing e. aberration 11. Infrared astronomy is often done from high-flying aircraft because a. infrared telescopes only need to get above the ozone layer. * b. infrared radiation is absorbed low in Earth's atmosphere. c. infrared photons are quite energetic. d. infrared telescopes are not very heavy. e. infrared sources are very bright. 12. The technique called uses a high-speed computer to monitor atmospheric distortion and adjust the optics of a telescope to partially compensate for the seeing. a. photometry b. chromatic aberration c. active optics d. spherical aberration * e. adaptive optics 13. The of a telescope is a measure of its ability to show fine detail and depends on the diameter of the objective. a. light-gathering power 2
b. focal length c. magnifying power * d. resolving power 14. A telescope that suffers from chromatic aberration and has a low light gathering power is most likely a. a small diameter reflecting telescope. * b. a small diameter refracting telescope. c. a large diameter refracting telescope. d. a large diameter reflecting telescope. e. the Hubble Space Telescope. 15. What is the ratio of the light gathering power of a 5-m telescope to that of a 0.5-m telescope? a. 10 b. 0.1 c. 0.01 * d. 100 e. 25 16. What is the magnification of a telescope and eyepiece if the telescope objective has a focal length of 200 cm and the eyepiece has a focal length of 0.2 cm? a. 400 times b. 4000 times * c. 100 times d. 1000 times e. 40 times 17. The resolving power of a telescope with a diameter of 232 cm is * a. 0.05 arc seconds. b. 232 arc seconds. c. 2.32 arc seconds. d. 5 arc seconds. e. 11.6 arc seconds. 18. CCD stands for a a. photometer. * b. charge-coupled device. c. spectrograph. d. core collapse device. e. grating. 19. Observations of radio waves from astronomical objects suffer from poorer resolution than visible observations because a. the signals are so weak in the radio region. * b. the wavelength of radio waves is much longer than the wavelengths of visible light. c. radio telescopes are generally much smaller in diameter than optical telescopes. d. it is very difficult to detect radio waves. e. radio telescopes don t use solid mirrors. 3
20. Radio telescopes have poor resolving power because a. their diameters are so large. b. the energy they receive is not electromagnetic radiation. * c. radio waves have long wavelengths. d. a and b e. none of the above 21. penetrate(s) the Earth s atmosphere to reach its surface. a. X-rays b. Radio waves c. Visible light d. Answers a and b * e. Answers b and c 22. The Hubble Space Telescope objective mirror is not affected by a. bad seeing. b. chromatic aberration. c. diffraction. d. Answers b and c * e. Answers a and b 23. The Spitzer Space Telescope orbits very far from Earth because the Earth thermally emits at which the telescope is also constructed to observe. * a. infra-red radiation b. radio waves c. X-waves d. gamma rays e. all of the above 24. The main reason for building large optical telescopes on the Earth's surface is a. that there is a lot of money in science that needs to get spent. * b. to collect as much light as possible from faint objects. c. to nullify the blurring effects of the Earth's atmosphere and thus produce higher resolution images. d. to bring astronomical objects closer to make them brighter. e. that the warm temperatures of the Earth s surface allow for easier telescope operation. 25. What statement below best describes the refraction of light? a. The absorption of light as it travels though a dense, transparent material. b. The spreading out of white light according to wavelength. * c. The change in direction of a light ray as it passes to a medium of different optical density. d. The change in direction of a ray of light as it reflects off a surface. 26. The light-gathering power of a telescope is directly proportional to * a. the diameter of the primary mirror or lens. b. the focal length of the primary mirror or lens. 4
c. the ratio of the focal lengths of its primary mirror or lens and its eyepiece. d. the length of the telescope tube. e. the diameter of the eyepiece. 27. Chromatic aberration occurs in a telescope when a. reflecting; different colors of light do not focus at the same point. * b. refracting; different colors of light do not focus at the same point. c. reflecting; light of different wavelengths get absorbed by the mirror. d. refracting; light of different wavelengths get absorbed by the lens. 28. The main reason for positioning many radio telescopes across a large area and combining the signals is a. to observe more objects in a shorter amount of time. b. provide a backup system if one or more of the telescopes go down. * c. to produce higher resolution images. d. to avoid interference between signals from the separate telescopes. e. to account for the motion of objects in the sky as a result of the Earth s rotation. 29. Radio telescopes are telescopes. * a. Reflecting b. Refracting c. Deflecting d. Compound e. Retracting 30. A telescope whose objective is a lens and contains no mirrors is a(n) telescope. * a. Refracting b. Reflecting c. Deflecting d. Compound e. Retracting 31. In a reflecting telescope the objective is a. a. prism * b. mirror c. lens d. diffraction grating e. photographic plate 32. Which has the larger light-gathering power? a. A telescope of 5 cm diameter and focal length of 50 cm. * b. A telescope of 6 cm diameter and focal length of 100 cm. c. A telescope of 2 cm diameter and focal length of 100 cm. d. A telescope of 3 cm diameter and focal length of 75 cm. e. Both b and c since they have the same focal length 33. The resolving power of a telescope is. 5
* a. a measure of the minimum angular separation that can be seen with the telescope. b. a measure of the maximum angular separation that can be seen with the telescope. c. a measure of the amount of light that the telescope can gather in one second. d. the separation between the objective and the image. e. a measure of how blurry object appear in the telescope. 6