Astronomy Ch. 6 Practice Questions
What does angular resolution measure?
The angular size of the smallest features that the telescope can see.
Which of the following telescopes benefits most from adaptive optics?
The Keck I telescope on Mauna Kea
Which of the following statements best describes the difference between a refracting telescope and a reflecting telescope?
A refracting telescope uses a transparent glass lens to focus light while a reflecting telescope uses a mirror to focus light.
The stars in our sky twinkle in brightness and color because of ______.
turbulence in the Earth's atmosphere
Which of the following is not one of the three main categories of observation generally used by astronomers?
Filtering to look at just a single color from an object.
Which of the following best describes why radio telescopes are generally much larger in size than telescopes designed to collect visible light?
Getting an image of the same angular resolution requires a much larger telescope for radio waves than for visible light.
Suppose you want to determine the chemical composition of a distant planet or star. Which of the following will be most useful to have?
High spectral resolution.
What is the purpose of interferometry?
It allows two or more small telescopes to achieve the angular resolution of a much larger telescope.
What is the purpose of adaptive optics?
It reduces blurring caused by atmospheric turbulence for telescopes on the ground.
Which of the following is not an advantage of the Hubble Space Telescope over ground-based telescopes?
It is closer to the stars.
What do we mean by the diffraction limit of a telescope?
It is the angular resolution the telescope could achieve if nothing besides the size of its light-collecting area affected the quality of its images.
Which of the following best describes what we mean by the focal plane of a telescope?
It is the place where, if we mounted film or an electronic detector, we could get a clear (not blurry) image of an object viewed through the telescope.
What do astronomers mean by light pollution?
Light pollution is light from human sources that makes it difficult to see the stars at night.
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.)
Observatory X can detect dimmer stars and Observatory Y reveals more detail in images.
Which of the following studies is best suited to astronomical observations that fall into the category called time monitoring?
Studying how a star's brightness varies over a period of 3 years.
Which of the following statements best describes the two principle advantages of telescopes over eyes?
Telescopes can collect far more light with far better angular resolution.
How does the light-collecting area of an 8-meter telescope compare to that of a 2-meter telescope?
The 8-meter telescope has 16 times the light-collecting area of the 2-meter telescope.
Why does the Sun's image look distorted in shape at sunset?
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 while the other one becomes fuzzy (grainy) looking. Which of the following statements is true?
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?
The photo will seem to show only one star rather than two.
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?
The thin air on mountaintops makes the glass in telescope mirrors less susceptible to warping.
Which of the following best describes the development of astronomical telescopes over the past 65 years?
The world's most powerful telescope remained the same for most of this period, but in the past 20 years many new and more powerful telescopes have been built.
Which of the following is always true about images captured with X-ray telescopes?
They are always shown with colors that are not the true colors of the objects that were photographed.
Why can't X-ray and gamma-ray telescopes use the same designs as visible-light telescopes?
X rays and gamma rays have so much energy that they cannot be reflected in the same way as visible light.
The Chandra X-ray Observatory must operate in space because:
X rays do not penetrate Earth's atmosphere.
Suppose you have a camera attached to a telescope, and you want to record an image of a very faint galaxy. Which of the following will help the most?
a lot of pixels and a long exposure time
What is the angular resolution of the human eye?
about 1 arcminute, or 1/60 of a degree
Which of the following wavelength regions can be studied with telescopes on the ground?
radio, visible, and very limited portions of the infrared and ultraviolet regions
When your eye forms an image, the _____ plays a role analogous to the detector in a camera.
retina
Which of the following effects is caused by atmospheric turbulence?
twinkling of stars