Chapter 6: Telescopes (Concept Quiz)

Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light? A. Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light. B. Objects that emit radio waves are always much larger than objects that emit visible light, and therefore require larger telescopes. C. It is because radio telescopes are used in the daytime and visible light telescopes are used at night. D. Radio telescopes are designed to collect sound rather than light.

A. Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.

Why does the Sun's image look distorted in shape at sunset? A. The distortion arises because of the way air affects the paths of light. B. The distortion is an illusion that you notice by eye but does not show up in photographs. C. Air scatters different colors of light by different amounts. D. The distortion is an artifact of the photographic process that your eyes would not actually see.

A. The distortion arises because of the way air affects the paths of light.

Suppose you have two small photographs of the Moon. Although both look the same at small size, when you blow them up to poster size one of them still looks sharp, whereas the other one becomes fuzzy (grainy) looking. Which of the following statements is true? A. The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy. B. Both photographs have the same angular resolution because they are both photographs of the same object. C. Both photographs have the same angular resolution because they were both printed at the same sizes in each case. D. The one that looks fuzzy at large size has better angular resolution (smaller) than the one that looks sharp.

A. The one that still looks sharp at large size has better (smaller) angular resolution than the one that looks fuzzy.

The angular separation of two stars is 0.1 arcseconds and you photograph them with a telescope that has an angular resolution of 1 arcsecond. What will you see? A. The photo will seem to show only one star rather than two. B. The two stars will appear to be touching, looking rather like a small dumbbell. C. The stars will not show up at all in your photograph. D. You will see two distinct stars in your photograph.

A. The photo will seem to show only one star rather than two.

Consider two future observatories in space. Observatory X consists of a single 50-meter telescope. Observatory Y is an interferometer consisting of five 10-meter telescopes, spread out over a region 100 meters across. Which observatory can detect dimmer stars, and which one can see more detail in its images? (Assume all else is equal, such as quality of optics, types of instruments, and so on.) A. Observatory Y both detects dimmer stars and reveals more detail in images. B. Observatory X can detect dimmer stars, and Observatory Y reveals more detail in images. C. Both observatories have the same capabilities, but Observatory Y would be cheaper to build. D. Observatory X both detects dimmer stars and reveals more detail in images. E. Observatory Y can detect dimmer stars, and Observatory X reveals more detail in images.

B. Observatory X can detect dimmer stars, and Observatory Y reveals more detail in images.

The Chandra X-ray Observatory must operate in space because __________________________. A. X rays are too dangerous to be allowed on the ground B. X-ray telescopes require the use of grazing incidence mirrors C. it was built by NASA. D. X rays do not penetrate Earth's atmosphere

B. X-ray telescopes require the use of grazing incidence mirrors

Suppose you have a camera attached to a telescope, and you want to record an image of a faint galaxy. Which of the following will help the most? A. a lot of pixels and a short exposure time B. a lot of pixels and a long exposure time C. a small number of pixels and a short exposure time D. a small number of pixels and a long exposure time

B. a lot of pixels and a long exposure time

Which of the following telescopes benefits most from adaptive optics? A. The Arecibo radio telescope in Puerto Rico B. The Chandra X-ray Observatory C. The Keck I telescope on Mauna Kea D. The Hubble Space telescope

C. The Keck I telescope on Mauna Kea

Which of the following is not a reason why telescopes tend to be built on mountaintops that are relatively far from cities and are in regions with dry climates? A. Dry regions mean less rain and clouds, and mountaintops in dry regions may even allow some infrared observations. B. Being on a high mountain top means being relatively high in the atmosphere, which tends to limit turbulence. C. The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping. D. Mountaintops far from cities are generally subject to less light pollution than locations nearer to cities.

C. The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.

Why are astronomers interested in building observatories capable of detecting neutrinos, cosmic rays, and gravitational waves? A. These things should in principle be much easier to detect than light, which means we could build these observatories cheaply. B. These things are the highest energy forms of light, even more energetic than gamma rays, and therefore can tell us about explosive processes in the universe. C. These things are not forms of light, and therefore can provide different types of information than light about objects that emit them. D. These things are emitted from the same objects that emit X rays, but unlike X rays, they can be detected with observatories on the ground.

C. These things are not forms of light, and therefore can provide different types of information than light about objects that emit them.

Why can't X-ray and gamma-ray telescopes use the same designs as visible-light telescopes? A. X rays and gamma rays are so intense that they would melt the glass in a visible-light telescope. B. Visible-light telescopes can only reflect light that we see, not any other kind of light. C. X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light. D. X rays and gamma rays do not penetrate Earth's atmosphere.

C. X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.

Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes? A. Stars do not twinkle when observed from space. B. It never has to close because of cloudy skies. C. It can observe infrared and ultraviolet light, as well as visible light. D. It is closer to the stars.

D. It is closer to the stars.

Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring? A. Measuring the rotation rate of a distant star. B. Studying how different planets differ in their surface compositions. C. Determining the age of the solar system. D. Studying how a star's brightness varies over a period of 3 years.

D. Studying how a star's brightness varies over a period of 3 years.

How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope? A. The answer cannot be determined from the information given in the question. B. The 8-meter telescope has 4 times the light-collecting area of the 2-meter telescope. C. The 8-meter telescope has 8 times the light-collecting area of the 2-meter telescope. D. The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

D. The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.

The stars in our sky twinkle in brightness and color because of ______. A. light pollution B. rapid changes in the brightness and colors of stars caused by changes in their spectra C. the bubbling and boiling of gases on the surfaces of stars D. turbulence in the Earth's atmosphere

D. turbulence in the Earth's atmosphere