Problems for 15 April 1996

You can hand in the following problems at beginning of class on Monday 15 April. If you have more than one page, please staple them together. And don't forget to include your name. Also, please write at the top near your name that these are the problems for 15 April.

How do telescopes work?
- Reading: Chapter 6 Optics and Telescopes .
- Questions: 5,7,8,11,12,14,16.
More on light.
- Questions: S1 and S2 below.

Here are the questions:

5) Explain some of the advantages of reflecting telescopes over refracting telescopes.
7) Quite often advertisemehts appear for telescopes that extol their magnifying abilities. Is this a good criterion for evaluating telescopes? Explain your answer.
8) What kind of telescope would you use if you wanted to take a color photograph entirely free of chromatic aberation? Why?
11) Why can radio astronomers make observations at any time during the day, whereas optical astronomers are mostly limited to observing at night?
12) What are the optical window and the radio window? Why isn't there an X-ray window or an ultraviolet window?
14) Why must astronoomers use satellites and Earth-orbiting observatories to study the heavens at X-ray and gamma-ray wavelengths?
16) Compare the light-gathering power of the Palomar 5-m telescope with that of the fully dark-adapted human eye, which has a pupil diameter of about 5 mm.
S1) A certain kind of imaginary atom (Oregonium) has energy levels 19 eV 18 eV 15 eV 10 eV 0 eV Suppose that you have a single atom of Oregonium and it is in the 15 eV state. What are the energies of the photons that it can emit? What are the energies of the photons that it can absorb?
S2) The wavelength of the H-beta line is 486.113 nm. Suppose that you find the H-beta line in the spectra of several galaxies and measure the wavelenghts to be Galaxy A: 654.164 nm Galaxy B: 417.183 nm Galaxy C: 495.635 nm Galaxy D: 486.072 nm Which galaxies are moving away from us? Of those, which are moving away from us the fastest? Which are moving toward us. Of those, which are moving toward us the fastest?

Davison E. Soper, Institute of Theoretical Science, University of Oregon, Eugene OR 97403 USA soper@bovine.uoregon.edu