Light and Telescopes Chapter.4 Exam Questions - Understanding Our Universe 3e Complete Test Bank by Stacy Palen. DOCX document preview.
Chapter 4: Light and Telescopes
LEARNING OBJECTIVES
4.1 What Is Light?
4.1a Summarize the electromagnetic properties of light.
4.1b Relate color, wavelength, and energy of photons.
4.1c List the names and wavelength ranges of the electromagnetic spectrum.
4.2 Cameras and Spectrographs Record Astronomical Data
4.2a Compare the optical properties of the human eye to film or a CCD camera.
4.2b Explain why photographic plates and CCD cameras are important tools of the astronomer.
4.3 Telescopes Collect Light
4.3a Explain why telescopes are important astronomical tools.
4.3b Describe the processes of reflection and refraction.
4.3c Compare and contrast the design, construction, and optical characteristics of reflecting and refracting telescopes.
4.3d Relate light gathering power to telescope aperture.
4.3e Relate resolution to telescope aperture.
4.3f Explain when and why it is advantageous or necessary to place telescopes in space.
4.3g Explain the effects of atmospheric seeing.
Working It Out 4.1
Working It Out 4.1a Relate frequency and wavelength of a wave.
Working It Out 4.2
Working It Out 4.2a Calculate the diffraction limit of a telescope.
Chapter 4: Light and Telescopes
MULTIPLE CHOICE
1. The speed of light was first determined by which scientist?
a. Galileo d. Newton
b. Rømer e. Einstein
c. Kepler
2. The speed of light in a vacuum is
a. 300,000 miles per hour (mph).
b. 300,000,000 mph.
c. 300,000,000 kilometers per second (km/s).
d. 300,000,000 meters per second (m/s).
e. infinite.
3. How does the speed of light traveling through a medium (such as air or glass) compare to the speed of light in a vacuum?
a. It is the same as the speed of light in a vacuum.
b. It is always slightly less than the speed of light in a vacuum.
c. It is always slightly greater than the speed of light in a vacuum.
d. Sometimes it is greater than the speed of light in a vacuum, and sometimes it is less, depending on the medium.
4. The light-year is a unit of
a. time. c. speed.
b. distance. d. energy.
5. What wave property relates the number of cycles per second?
a. amplitude c. speed
b. wavelength d. frequency
6. What wave property is associated with the brightness of light?
a. amplitude c. speed
b. wavelength d. frequency
7. How do the wavelength and frequency of red light compare with the wavelength and frequency of blue light?
a. Red light has a longer wavelength and higher frequency than does blue light.
b. Red light has a longer wavelength and lower frequency than does blue light.
c. Red light has a shorter wavelength and higher frequency than does blue light.
d. Red light has a shorter wavelength and lower frequency than does blue light.
8. Which of the following lists different types of electromagnetic radiation in order of increasing wavelength?
a. radio waves, infrared, visible, ultraviolet, X-rays
b. gamma rays, ultraviolet, visible, infrared, radio waves
c. gamma rays, X-rays, infrared, visible, ultraviolet
d. X-rays, infrared, visible, ultraviolet, radio waves
e. radio waves, ultraviolet, visible, infrared, gamma rays
9. Which of the following lists different types of electromagnetic radiation in order of increasing frequency?
a. radio waves, infrared, visible, ultraviolet, X-rays
b. gamma rays, ultraviolet, visible, infrared, radio waves
c. gamma rays, X-rays, infrared, visible, ultraviolet
d. X-rays, infrared, visible, ultraviolet, radio waves
e. radio waves, ultraviolet, visible, infrared, gamma rays
10. Which of the following lists different types of electromagnetic radiation in order of increasing energy?
a. radio waves, infrared, visible, ultraviolet, X-rays
b. gamma rays, ultraviolet, visible, infrared, radio waves
c. gamma rays, X-rays, infrared, visible, ultraviolet
d. X-rays, infrared, visible, ultraviolet, radio waves
e. radio waves, ultraviolet, visible, infrared, gamma rays
11. Which of the following photons carry the least amount of energy?
a. a blue photon of the visible spectrum, whose wavelength is 450 nanometers (nm)
b. an infrared photon, whose wavelength is 10–5 meter
c. a red photon in the visible spectrum, whose wavelength is 700 nm
d. a microwave photon, whose wavelength is 10–2 meter
12. Which of the following photons carry the most amount of energy?
a. a blue photon of the visible spectrum, whose wavelength is 450 nm
b. an infrared photon, whose wavelength is 10–5 meter
c. a red photon in the visible spectrum, whose wavelength is 700 nm
d. a microwave photon, whose wavelength is 10–2 meter
13. A red photon has a wavelength of 650 nm. An ultraviolet photon has a wavelength of 250 nm. The energy of an ultraviolet photon is __________ than a red photon.
a. 2.6 times larger c. 2.6 times smaller
b. 6.8 times larger d. 6.8 times smaller
14. As wavelength increases, the energy of a photon __________ and its frequency __________.
a. increases; decreases c. decreases; decreases
b. increases; increases d. decreases; increases
15. As frequency increases, the energy of a photon __________ and its wavelength __________.
a. increases; decreases c. decreases; decreases
b. increases; increases d. decreases; increases
16. Using the following figure, which type of electromagnetic wave has a wavelength of approximately 10–5 meter?
a. X-rays c. microwave
b. infrared d. radio
17. Using the following figure, which type of electromagnetic wave has a frequency of approximately 3 
1017 Hz?
a. X-rays c. microwave
b. infrared d. radio
18. The Voyager 1 spacecraft is currently 20.7 billion km from Earth and heading out of our Solar System. How long does it take radio messages from Voyager 1 to reach us?
a. 1.9 days c. 1.9 weeks
b. 19.2 hours d. 19.2 minutes
19. What form of radiation can be felt by your skin as heat?
a. radio c. infrared
b. X-ray d. ultraviolet
20. Light with a wavelength of 600 nm has a frequency of
a. 5.0 106 hertz (Hz). c. 5.0 1011 Hz.
b. 5.0 1014 Hz. d. 2.0 1015 Hz.
21. If the wavelength of a beam of light were to double, how would that affect its frequency?
a. The frequency would be four times larger.
b. The frequency would be two times larger.
c. The frequency would be two times smaller.
d. The frequency would be four times smaller.
e. There is no relationship between wavelength and frequency.
22. If the frequency of a beam of light were to double, how would that affect its wavelength?
a. The wavelength would be four times larger.
b. The wavelength would be two times larger.
c. The wavelength would be two times smaller.
d. The wavelength would be four times smaller.
e. There is no relationship between wavelength and frequency.
23. Which formula denotes how the speed of light is related to its wavelength and frequency?
a. c 
f c. c f /
b. c /f d. c 1/f
24. Before charge-coupled devices (CCDs) were invented, what was the device most commonly used for imaging with optical telescopes?
a. Polaroid cameras c. high-speed film
b. photographic glass plates d. video cameras
25. The fact that the speed of light is constant (as it travels through a vacuum) means that
a. photons with longer wavelengths have lower frequencies.
b. radio wave photons have shorter wavelengths than gamma-ray photons.
c. X-rays can be transmitted through the atmosphere around the world.
d. All choices are true.
26. List two optical properties found in human eyes and all other astronomical detectors.
a. integration time and wavelength sensitivity
b. quantum efficiency and integration time
c. wavelength sensitivity and signal strength
d. quantum efficiency and signal strength
27. The part of the human eye that acts as the detector is the
a. retina. c. rod.
b. pupil. d. cone.
28. The part of the human eye that acts as the aperture is the
a. retina. c. rod.
b. pupil. d. cone.
29. The most important improvement that photography provides over naked-eye observations is
a. it is possible to observe a larger field of view with photographic plates.
b. the quantum efficiency is higher for photographic plates.
c. the image resolution is much better for photographic plates.
d. longer integration times that detect fainter objects with the use of photographic plates.
30. The major advantage CCDs have over other imaging techniques is that
a. they have a higher quantum efficiency.
b. they have a linear response to light.
c. they yield output in digital format.
d. they operate at visible and near-infrared wavelengths.
e. All choices are true.
31. One reason to prefer a reflecting over a refracting telescope is its
a. lack of chromatic aberration.
b. shorter length for the same aperture size.
c. lighter weight for larger apertures.
d. All choices are valid reasons.
32. The blurring of point sources like stars seen through a space telescope is due to
a. reflection. c. scattering.
b. seeing. d. diffraction.
33. Arrays of radio telescopes can produce much better resolution than single-dish telescopes because they work based on the principle of
a. reflection. c. diffraction.
b. refraction. d. interference.
34. When we determine the angular resolution of an interferometric array of radio telescopes using the formula 
/D, the variable D stands for the
a. diameter of the telescopes. c. number of telescopes.
b. separation between the telescopes. d. focal length of the telescopes.
35. Which of the following causes the biggest problem in detecting infrared photons from an astronomical object?
a. smog c. water vapor
b. carbon dioxide d. light pollution
36. The speed of a light wave
a. is altered by a refractive medium.
b. is reduced whenever reflection occurs.
c. remains constant during reflection or refraction.
d. remains constant through the boundary where refraction takes place.
37. Why do reflecting telescopes usually have a secondary mirror in addition to a primary mirror?
a. to increase the light-gathering power c. to improve resolution
b. to make the telescope shorter d. to combat chromatic aberration
38. As a beam of light travels from one medium to another, the change in direction of the beam of light depends on
a. the wavelength of the light.
b. the angle of incidence.
c. the index of refraction of the medium into which it is moving.
d. All choices are true.
39. How does the resolving power of a telescope depend on its focal length?
a. The longer the focal length is, the better the resolving power is.
b. The longer the focal length is, the worse the resolving power is.
c. There is no relation between resolving power and focal length.
d. The shorter the focal length is, the better the resolving power is.
40. The angular resolution of a ground-based telescope is usually set by
a. diffraction. c. the focal length.
b. refraction. d. atmospheric seeing.
41. Telescopes that use adaptive optics provide higher spatial resolution images primarily because
a. they operate above Earth’s atmosphere.
b. they capture infrared light, which has a longer wavelength than visible light.
c. deformable mirrors are used to correct the blurring as a result of Earth’s atmosphere.
d. composite lenses correct for chromatic aberration.
42. The 500-meter FAST radio telescope in China observing wavelengths of 0.1m has a resolution that is closest to that of
a. the Hubble Space Telescope (0.1 arcsecond [arcsec]).
b. a human eye (1 arcminute [arcmin]).
c. the Chandra X-ray Observatory (0.5 arcsec).
d. a 1-meter optical telescope (1 arcsec).
43. Ultraviolet radiation is hard to observe primarily because
a. Earth’s atmosphere easily absorbs it.
b. no space-based telescopes operate at ultraviolet wavelengths.
c. only the lowest-mass stars emit ultraviolet light.
d. very few objects emit at ultraviolet wavelengths.
44. Which of the following properties is (are) improved by placing telescopes in space?
a. quantum efficiency
b. integration time and angular resolution
c. quantum efficiency and integration time
d. ability to observe at any wavelength region and angular resolution
45. Both reflecting and refracting telescopes suffer from
a. chromatic aberration.
b. diffraction effects and chromatic aberration.
c. deformation of optics at large apertures.
d. diffraction effects.
46. How does the light-gathering power of a 4-meter telescope compare to that of a 2-meter telescope?
a. More light is collected.
b. Less light is collected.
c. They collect the same amount of light.
d. It depends if the telescope is refracting or reflecting.
47. The SETI project’s Allen Telescope Array will have 350 radio dishes, each with an individual diameter of 6 meters, spread out over a circle whose diameter is 1 km. What would this array’s spatial resolution be when it operates at 5 cm?
a. 10 arcsec c. 10 arcmin
b. 0.10 arcsec d. 1.0 arcmin
48. The two Keck 10-meter telescopes, separated by a distance of 85 meters, can operate as an interferometer. What is its resolution when it observes in the infrared at a wavelength of 2 micrometers (μm)?
a. 0.01 arcsec c. 0.05 arcsec
b. 0.005 arcsec d. 0.2 arcsec
49. The diffraction limit of a 4-meter telescope is __________ than that of a 1-meter telescope.
a. two times larger c. two times smaller
b. four times larger d. four times smaller
50. The angular resolution of the largest single-dish radio telescope in the United States, the 100-meter Green Bank Telescope, is closest to __________ when it operates at a wavelength of 20 centimeters (cm).
a. 0.6
c. 412 arcsec
b. 20 arcmin d. 500 arcsec
1. What is the fundamental constant, c, and where is it applicable?
2. Compare and contrast the wavelengths, frequencies, speeds, and energies of red and blue photons.
3. Using the following figure, fill in the blanks and label the different regions of the electromagnetic spectrum.
4. Using the following figure, list the different types of electromagnetic waves in order of decreasing frequency.
5. Give an explanation as to why electromagnetic radiation does not require a medium for propagation.
6. Explain two major advantages of CCDs over other imaging techniques.
7. Explain why the largest telescopes are not refracting telescopes.
8. Explain why stars twinkle when viewed from the ground. Would they twinkle if viewed from outer space?
9. Explain how adaptive optics help compensate for atmospheric seeing.
10. What type of telescope is shown in the following image?
11. Describe what is shown in the following image.
12. Discuss two tools that modern astronomers use to explore the cosmos that are different from traditional optical telescopes, and give an example of how and why each is used.
13. The following image shows the Very Large Array in New Mexico. What is the benefit of using multiple telescopes in such an array?
14. How do telescopes advance astronomical science?
15. Where should telescopes purposed to observe the high-energy light from the death of stars be located?
16. Why is the wavelength of a reflected light wave generally equal to that of the incident wave?
17. What is meant if a substance has a higher index of refraction?
18. What is the angular resolution of a 1-meter, ground-based, optical telescope that observes at a wavelength of 600 nm compared with that of a 300-ft, single-dish radio telescope that observes at a wavelength of 21 cm?
19. Describe the optical system depicted, and label the components (A, B, C) and their functions.
20. A salesman tells you that he has 8-inch telescopes for sale. What feature of the telescope is described by this measurement? Label the described feature in the following image.
21. Describe the optical systems depicted, and describe the differences between the two.
(a)
(b)
22. What is the diffraction limit of a 2-meter telescope observing at a wavelength of 650 nm?