Describe reflection and refraction. How do these processes enable astronomers to build telescopes?
Give everyday examples of refraction and reflection.
Which side of the secondary mirror in Figure 3-
Explain some of the advantages of reflecting telescopes over refracting telescopes.
What are the three major functions of a telescope?
What is meant by the angular resolution of a telescope?
Why will many of the very large telescopes of the future make use of multiple mirrors?
What is meant by adaptive optics? What problem does adaptive optics overcome?
Compare an optical reflecting telescope to a radio telescope. What do they have in common? How are they different?
Why can radio astronomers observe at any time of the day or night, whereas optical astronomers are mostly limited to observing at night?
Why must astronomers use satellites and Earth-
What are NASA’s four Great Observatories, and in what parts of the electromagnetic spectrum do (or did) they observe?
Why did Rømer’s observations of the eclipses of Jupiter’s moons support the heliocentric, but not the geocentric, cosmology?
A blackbody glowing with which of the following colors is coolest?
yellow
red
violet
orange
blue
Of the following photons, which has the highest energy?
a. infrared
b. radio waves
c. visible light
d. X-
e. ultraviolet
The spectrum of which of the following objects will show a redshift?
an object moving just eastward on the celestial sphere
an object moving just northward on the celestial sphere
an object moving directly toward Earth
an object moving directly away from Earth
an object that is not moving relative to Earth
What is a blackbody? What does it mean to say that a star appears almost like a blackbody? If stars appear to be like blackbodies, why are they not black?
What is Wien’s law? How could you use it to determine the temperature of a star’s surface?
What is the Stefan-
Using Wien’s law and the Stefan-
What is an element? List the names of five different elements, and briefly explain what makes them different from each other.
How are the three isotopes of hydrogen different from each other?
Why do different elements have different patterns of lines in their spectra?
What is the Doppler shift, and why is it important to astronomers?
Explain why the Doppler shift tells us only about the motion directly along the line of sight between a light source and an observer but not about motion across the celestial sphere.
Why do stars twinkle?
Why do all research telescopes use primary mirrors rather than objective lenses?
For the purpose of observing very faint objects, which of the following features of a telescope is most important? Explain your answer.
its maximum magnification
its ability to resolve colors
the size of its objective lens or primary mirror
the type of mount it has
its weight
Of the following types of electromagnetic radiation, which is most dangerous to life?
radio waves
X-
ultraviolet radiation
infrared radiation
visible light
What color does the Sun emit most intensely?
A star of which of the following colors is hottest?
blue
red
orange
yellow
white
If a yellow star cools off, what color will it become next?
Advertisements for home telescopes frequently give a magnification for the instrument. Is this a good criterion for evaluating such telescopes? Explain your answer.
Show by means of a diagram why the image formed by a simple refracting telescope is “upside down.”
Why does no major observatory have a Newtonian reflector as its primary instrument, whereas Newtonian reflectors are popular among amateur astronomers?
Why will many of the very large telescopes of the future have ultrathin primary mirrors?
What color will an interstellar gas cloud composed of hydrogen glow, and why?
Explain how the spectrum of hydrogen is related to the structure of the hydrogen atom.
Do we see all the colors from each star? Why or why not?
Discuss the advantages and disadvantages of using a relatively small visible-
If you were in charge of selecting a site for a new observatory, what factors would you consider?
Consider two identical Cassegrain telescope mirrors. One is set up as a prime focus telescope, whereas the other is used in a Cassegrain telescope.
Sketch both telescopes.
What are the differences between the two that make each useful in different observing situations?
Compare the technique of identifying chemicals by their spectral line patterns with that of identifying people by their fingerprints.
Suppose you look up at the night sky and observe some of the brightest stars with your naked eye or binoculars. Is there any way of telling which stars are hotter and which are cooler? Explain your answer.
How could we exclude Earth’s atmosphere as the source of the iron absorption lines in Figure 3-