Fall 2000 ASTR 1120-001 Review for Quiz 1

The quiz will contain 10 multiple-choice questions, and will be 10 minutes long. The intention is that all material on the quiz (saving matters of logic and common sense) is referred to somewhere here.

1. Estimation. What is an order of magnitude? How does order of magnitude estimation work? Think up an example of where you might apply order of magnitude estimation in astronomy.

2. Distances in Astronomy. Name two measures of distance commonly used by astronomers. What do these measures signify? Describe how trigonometric parallax works. Who first measured the Astronomical Unit, and how? Who measured the first distance to a star, and how?

3. Looking back. When we look deeper into space, we are looking back further in time. Explain. Be quantitative.

4. Escape velocity. What does gravitational escape velocity mean? What does the speed at which modern spacecraft go have to do with the gravitational escape velocity from Earth?

5. The Nature of Light. What is light? Is it a force? A form of electricity? A form of energy? What has light got to do with electricity and magnetism? Is light a particle or a wave? When does light behave like a wave, and when does it behave like a particle? What phenomena show that light is a wave? What phenomena show that light is a particle? What quantitative properties does light have? How are these quantitative properties related?

6. Types of Light. Radio waves are a kind of `light'. What other kinds of `light' are there, and in what respects do they differ from each other? What kinds of light can you see? What kinds of light can you feel? What kinds of light can you hear? What kinds of light penetrate the Earth's atmosphere?

7. Spectrum. What does spectrum mean? What is the difference between emission lines and absorption lines? Draw pictures illustrating setups which might allow you to observe (a) emission lines, and (b) absorption lines from a substance.

8. Planck or Blackbody Spectrum. What is a Planck, or blackbody, spectrum (Bennett refers to radiation emitted with a blackbody spectrum as thermal radiation)? Under what circumstances would you expect something to have a Planck spectrum? How is the spectrum related to temperature? What is Wien's Law? How is the spectrum related to color? Is a red star hotter than a blue star or vice versa?

9. Energy levels of atoms. Why can electrons occupy only orbits with certain specific energies? Does the same principle apply to the solar system? Draw a schematic diagram of the energy levels of a hydrogen atom. How many levels are there? Draw processes corresponding to (a) emission, (b) absorption, (c) ionization, (d) recombination. Are the wavelengths/frequencies of emission lines the same as absorption lines? How is the frequency related to the energy levels of the emitting/absorbing atom?