Astronomy 100
EXAM 2 STUDY GUIDE

EXAM DATE:  Tuesday April 24th (Tuesday evening class)
                         Wednesday April 25th (MW classes)
TIME:   Be prompt, the exam will start at the beginning of class and will last one hour only.
MATERIAL COVERED:  * TEXTBOOK UNITS: 21, 22, 23, 24, 26, 27, 28, 29, 30, 52, 54, 55, 56, 57
                                             (consult your reading list to see what sections of each unit is covered)
                                         * LECTURE NOTES:  Pages 20 - 48, READING ASSIGNMENT #1

The second exam will test your comprehension of the following subjects:

The Nature of Light:

• the speed of light (how was it determined?  what are the implications of it being finite in speed?)
• the nature of light (particle-like or wave-like? What were some of the experiments to show each quality?)
• the colors of the rainbow - more accurately known as the "visible spectrum" (know the names and order of the colors)
• electromagnetic radiation (what is it? how is it made?)
• wave mechanics (wavelength vs. frequency, units: angstroms and hertz, how are frequency and wavelength related?)
• the electromagnetic spectrum (know the names of each realm.  What distinguishes the different "types" of electromagnetic radiation?)
• blackbody radiation (what is it?  what are the "rules"?  why is it useful to astronomers?)
• Wien's Law (what does this law say? how does it relate to objects behaving like blackbodies? why is it useful to astronomers?  how does it determine the temperatures of objects in nature?)
• spectral lines... what do you observe? (continuous lines, absorption lines, emission lines)
• what conditions produce each type of spectral line? (Know Kirchhoff's Laws and be able to apply the knowledge)
• how are spectral lines created? (electrons, protons, and neutrons oh my!)
• what can spectral lines tell you about stars? (temperatures, chemical compositions, physical conditions....etc)

Telescopes:

• why do we use telescopes? (what are "light-gathering-power" and "resolution"?)
• refracting vs. reflecting telescopes (how are they different?  which ones are better?  why?)
• why do we need space telescopes?
• where do astronomers build observatories?  what factors must they consider?

(BE SURE TO READ THE HANDOUT "READING ASSIGNMENT #1" THAT ACCOMPANIES THE SECTION ON TELESCOPES.  THERE WILL BE SEVERAL QUESTIONS ON THE EXAM FROM THIS ASSIGNMENT)

Stellar Properties:

• luminosity vs. brightness (what is the difference?)
• the apparent magnitude system (how is it quantified? Know how the apparent magnitude scale works)
• apparent magnitude vs. absolute magnitude (how are they different?)
• measuring stellar mass (know about binary stars and how they reveal stellar masses)
• determining stellar radius (the Temperature-Radius-Luminosity relationship)
• the Mass-Luminosity relationship (what does it mean?  how can it be helpful to knowing stellar properties?)
• Trigonometric Parallax (how does this concept determine the distances to stars?)

The following is a list of examples of the types of essay questions that will be asked on the exam:

1.  List and describe each of the factors that are considered by astronomers in choosing the best location for an astronomical observatory.

2.  Give a detailed explanation as to why astronomers require large telescopes (rather than small ones) for their work.

3.  What is the difference between refracting and reflecting telescopes?   Which one is preferred by astronomers?  Why?

4.  List the physical properties of stars that can be determined and briefly describe how each one is measured by astronomers.

The emphasis of this class is to teach you the nature of the universe around you. My expectations of you are that you understand the concepts that are discussed in class and that you can apply that knowledge. The role of this exam is to give you a chance to demonstrate your comprehension of the concepts, rather than simply restating memorized facts or definitions.

To do well on the exam you should be able to:

• Understand the relationships between the physical values in the important equations i.e. how does a change in one value affect another? For example, how does the wavelength of light determine the frequency of the light?  How does the change in temperature affect the change in wavelength of peak emission of a blackbody?  How does the luminosity of a star help determine the size of the star? Etc.

• Understand the definitions of the terminology that is used in the lectures. If you cannot understand the terminology, you cannot be expected to understand the basic concepts.

• Relate the various concepts to one another. For example, how does the wavelength of light relate to how an electron changes its orbital level?  How do observations of stellar spectral lines help us understand the masses of the stars? How does the color of a star relate to its temperature?  Etc.

• See the BIG PICTURE. If you feel that we have been spending much of our time going over seemingly unrelated ideas, then you are missing the BIG PICTURE.  Sit down and put the topics into perspective, get a feel for how the concepts are related.

• Read the textbook.  The reading list is provided to you in your course syllabus.

• Concentrate your studies on the lecture notes.  The textbook should also be read to help enhance your understanding of the lecture material.  Avoid reading more than one chapter of the textbook at a time.  A good approach is to read one chapter of the text each day while reviewing the class lecture notes simultaneously with that unit.

• Use the "Test Yourself" review questions at the end of each unit in the book to test whether or not you have a good understanding of the basic concepts.  The answers are in the back of the book.

• Don't try and study all of the material in one study session.  Spread it out over several days (of course this means that you should begin to study several days in advance).

Don't spend your valuable time doing the following: