Download Page 144 QUESTIONS FOR REVIEW 1. (5.1) What is light

Page 144
QUESTIONS FOR REVIEW
1.
(5.1) What is light-gathering power? How does it affect the ability to see faint objects?
2.
(5.1) What is the difference between a reflecting and a refracting telescope? What are some advantages
of a reflecting telescope? Which type are the biggest telescopes?
3.
(5.2) What is resolution of a telescope? What physical process limits it?
4.
(5.2) How is resolution affected by the size of a telescope's mirror or lens?
5.
(5.2) What is the purpose of an interferometer?
6.
(5.3) What is a CCD and how is it better than film?
7.
(5.4) Why do astronomers put X-ray observatories in space rather than just on high mountains?
8.
(5.4) What kinds of astronomy can be done from the ground?
9.
(5.4) What is meant by adaptive optics?
10.
(5.5) How do astronomers get to use observatories?
TEST YOURSELF
1.
(5.1) Telescope A's mirror has four times the diameter of telescope B's. How much greater is A's lightgathering power?
(a)
4 times
(b)
8 times
(c)
16 times
(d)
64 times.
(e)
2 times
2.
(5.2) A telescope's resolving power measures its ability to see?
(a)
fainter sources
(b)
more distant sources
(c)
finer details in sources
(d)
larger sources
(e)
more rapidly moving sources.
3.
(5.2) One way to increase the resolving power of a telescope is to?
(a)
make its mirror bigger
(b)
make its mirror smaller
(c)
replace its mirror with a lens of the same diameter
(d)
use a mirror made of gold
(e)
observe objects using longer wavelengths.
4.
(5.2) Astronomers use interferometers to?
(a)
observe extremely dim sources
(b)
measure the speed of remote objects
(c)
detect radiation that otherwise cannot pass through our atmosphere
(d)
enhance the resolving power (see fine details) in sources
(e)
measure accurately the composition of sources.
5.
(5.3) Which of the following are advantages of a CCD over photographic film? (Select all that are
correct?
(a)
CCDs can collect light for a long time
(b)
CCDs do not need to be changed out for each exposure.
(c)
CCDs are not affected by blurring of the Earth's atmosphere
(d)
CCDs do not need to be corrected for instrumental effects
(e)
CCDs record a greater percentage of the photons striking them.
6.
(5.1/5.3) Suppose you were examining a pulsing radio signal from a stellar remnant in a distant part of
the Milky Way. Knowing that ionized gas in interstellar space causes dispersion of radio waves, what
effect would you expect this to have on the signal?
(a)
The time when the pulses arrived would be different for different wavelengths
(b)
The path would be bent so the signal would come from a different direction than it started from
(c)
The wavelengths would all grow longer as they ran out of energy
(d)
The signal would be slowed down—stretched out to fill a much longer time.
7.
(5.4) To use ground-based optical telescopes to their theoretical specifications, astronomers must use?
(a)
much larger mirrors than we have today
(b)
adjustable mirrors that can adapt to correct for the atmosphere.
(c)
far more sensitive detectors.
(d)
space satellite surveys to plan observations.
8.
(5.5) Atmospheric refraction makes the Sun look?
(a)
smaller in diameter
(b)
more luminous
(c)
bluer in color
(d)
higher in the sky.
9.
(5.5) The purpose of adaptive optics is to make telescopes?
(a)
more flexible so they can fit in smaller buildings
(b)
look in several directions without having to move the primary mirror
(c)
capture more photons within their aperture.
(d)
adjust for the distortions caused by the Earth's atmosphere.
(e)
All of the above.