AST 1001 Introductory Astronomy I Study Guide for Exam #2 This ...

AST 1001
Introductory Astronomy I
Study Guide for Exam #2
This exam will consist of 50 to 100 multiple-choice questions. Questions will be drawn mainly
from lecture notes, with some questions coming from lab exercises and handouts, homework
exercises, and from Chapters 6, 7, and parts of 5 (orbits, tides) of the book. Most equations and
constants will be provided. Bring pencils and an eraser!
=====================================================================
ORBITS AND TIDES
(0) We covered a few items regarding orbits and tides, from Chapter 5, right after the first
exam. Be sure to review your notes and know such concepts as low-earth orbit,
synchronous orbit, conic sections, escape velocity, differential gravitational forces, spring
tides, neap tides, earth tides, relative importance of sun and moon in those. Are births
related to the Moon?
LIGHT AND THE ELECTROMAGNETIC SPECTRUM
(1) You should understand the electromagnetic wave model for light, that it is a transverse
wave in the electric and magnetic fields. You should understand the terminology for
waves--frequency, wavelength, velocity, and the equation relating them.
(2) Be familiar with the photon concept of light--how light interacts with matter one photon at
a time and that the energy of the photon is proportional to the frequency.
(3) You should know the order of the electromagnetic spectrum (gamma rays, X-rays, UV,
etc.), and which are longer wavelength (or lower frequency) than which others, etc. Do
not memorize any particular actual wavelengths except for the range of visible light (in
Angstroms) -- you should know this!
(4) You should know how light is dimmed according to the inverse square law, as discussed
in the book, and be able to do a simple calculation.
(5) Know what the Doppler effect is and how it changes the wavelength of light.
OPTICS & THE OPTICS OF TELESCOPES
(6) You should understand how light refracts when it encounters a boundary between two
materials of different index of refraction (what is the definition of n?). Know which way it
refracts with respect to the "normal" line when going from a region of higher n to lower n
(and vice versa). You should understand the argument for this directional change as based
on our diagram of wavefronts hitting the boundary at an angle. Know that dispersion
occurs because n is a function of ë.
(7) You should understand how rays refract through a simple positive or negative lens, and be
able to sketch the ray diagrams. Know what the focal length is for a lens or mirror.

(8) You should understand the basics of the law of reflection and how reflective optics work.
(9) You should know the optical causes and characteristics of familiar natural phenomena
such as rainbows and the halo sometimes seen around the sun or moon.
(10) You should be able to sketch the optical path of a simple refracting (lens) telescope and
the several types of reflecting (mirror) telescopes we discussed in class (Newtonian,
Cassegrain, prime focus, etc.). You should know what the optical problems are for
telescopes (aberrations, etc.), and why all very large telescopes are reflectors. Know that
we build large diameter telescopes for increased light-gathering power and angular
resolution, NOT for increased magnification. You should also know that the lightgathering
power of a telescope is proportional to the objective lens or mirror's area, which
is proportional to the diameter squared. Know how to calculate the magnification of a
telescope.
TELESCOPES O' THE WORLD
(11) You should know something of the history of the development of telescopes--the
contributions of Galileo, Newton, Jansky.
(12) You should be familiar with the major optical telescopes in current use, such as those at
Mt. Palomar, Kitt Peak, Cerro Tololo, Manua Kea, etc.). That is, know where the largest
telescopes are (as well as why they are there), and their diameters (largest reflector and
largest refractor).
(13) You should understand that modern observational astronomy does not rely on visual
observing but on instrumentation such as spectrographs and CCDs. Know that perhaps
the most commonly used tool is the computer!
(14) You should be familiar with the major radio telescopes of the world (Green Bank/NRAO,
VLA, VLBI). Who started radio astronomy? Understand the reasons that radio
telescopes are much larger than optical telescopes (Rayleigh's criterion and the energy of a
photon), and how interferometry is used to increase the angular resolution of radio arrays.
(15) Know what the major astronomical satellites are/were/will be (IUE, IRAS, Hubble Space
Telescope, and Chandra), and why we use satellites to observe. Know their general
properties (region of the spectrum, etc.).
PHYSICAL PROCESSES
(16) Know what the most common two elements are in our Universe and solar system, and
how the rest comprise a small (how small?) percentage of the abundances.
(17) You should understand how temperature is the measure of the speed of gases, and how
that, coupled with the concept of escape velocity, explains the gasses we find on the
different planets. Understand how the pressure of an atmosphere declines with increasing
altitude.

(18) You should know that blackbody (thermal) radiation is given off by all objects. You
should know what the intensity (brightness) vs. wavelength diagram looks like for a
blackbody and how it changes as the temperature of the blackbody changes. You should
understand that the total energy given off by a blackbody is proportional to T 4 (Stefan-
Boltzmann Law), and be able to calculate simple changes in this energy output for
changes in temperature (e.g., if the two blackbodies differ in temperature by a factor of 2
then their energy output differs by 2 4 = 2 x 2 x 2 x 2 = 16 ). You should understand that
the peak wavelength of the radiation curve is inversely proportional to the blackbody's
temperature (Wien’s Law.) Have an approximate idea of the peak wavelength of the
Sun and of an incandescent light bulb. Also, be familiar with temperature scales
(Fahrenheit, Celsius, Kelvin)--know what these are based on and their values for absolute
zero and the freezing and boiling points of water. Know that everything is in a balance of
absorption and emission of radiation–this is called thermal equilibrium.
(19) Understand the model of the atom and the concepts of nuclear fusion and fission. What
does Duke Power do? What do stars do? What is the half-life of an element and how is
that used to date things?
(20) You should understand how heat flows–by radiation, conduction, and convection.
LAB: You should understand the concepts and techniques developed in lab exercises that we
have done. You are responsible for all labs done, whether you were in attendance or not.
HOMEWORK:
Be able to do problems similar to those assigned as homework.
MISC.:
You should understand the causes of the moon's phases and the reason the Earth
experiences seasons. You should also be able to express a mathematical
computation’s result to the correct number of significant figures.