Chapter 5: Telescopes
Multiple Choice



1.  

How much more light would a 2-meter diameter telescope gather in a certain amount of time at a given wavelength compared with one that is 50 centimeters in diameter?



2.  

The planet Venus is often visible from central latitudes in the western evening sky or eastern morning sky, and does not appear to twinkle. The stars, however, do appear to twinkle. Why?



3.  

Astronomers use the term "seeing" to describe which of the following?



4.  

What is the primary reason that radio telescopes are easier to combine into interferometric arrays than optical telescopes?



5.  

What is the main reason that ultraviolet astronomy must be done in space?



6.  

What is meant in astronomy by the phrase "active optics"?



7.  

The "prime focus" of a telescope corresponds to which of the following locations?



8.  

What would be the best angular resolution for light in the visible region (say 500 nm) that we could expect from a department-store telescope whose primary lens or mirror is 5 cm in diameter?



9.  

What is meant by the "diffraction limited resolution" of a telescope?



10.  

Which of the following is not a characteristic of the indicated type of astronomy?



11.  

What would be the required diameter of the main mirror of a single large telescope in order to allow it to collect the same amount of light as six separate 4-m mirrors?



12.  

Large arrays of widely separated radio telescopes can achieve very good resolution. What is the primary reason that such good resolutions cannot be achieved by individual radio telescopes operating independently?



13.  

What is the optical configuration of a typical X-ray telescope?



14.  

If you combine the optical light-gathering capability of the two Keck telescope mirror arrays on Mauna Kea, each of which has the equivalent collecting area of a single mirror 10 meters in diameter, you would have an instrument equivalent in light-gathering capability to which of the following?



15.  

What is the optical configuration of a typical gamma-ray telescope?



16.  

The Andromeda galaxy lies about 700,000 pc away. What would be the size of a typical feature resolvable at this distance with a VLBI radio interferometer array that has an angular resolution 0.001 arc seconds?



17.  

Radio telescopes would not represent a good choice for astronomical study of which of the following types of object?



18.  

Which of the following describes the technique of adaptive optics?



19.  

Which of the following statements is true about the use of infrared telescopes?



20.  

A certain space-based telescope can achieve diffraction-limited angular resolution of 0.05 arc seconds for red light of wavelength 700 nm. What would be its resolution in the infrared at 3.5 microns?

Note: answer choices in this exercise are randomized.

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