Review for Exam I Chapters 1, 2, 3,4

1
Review for Exam IChapters 1, 2, 3,4

• PHYS 1050
• May, 2002

2
Purpose

• This document is a study guide, NOT a
  comprehensive list of all topics included on the
  exam.
• The exam will cover material from both the text
  and class notes.

3
Equations and Constants

• diameter/(2? x distance) angular diameter/360o
  
• small-angle formula diameter distance x
  (angular diameter/ 57.3o)
• F ma
• Fgrav Gm1m2/r2
• P2 a3
• speed of wave wavelength x frequency
• period 1/frequency
• energy of wave proportional to frequency (or
  1/wavelength)
• circumference of circle 2 ? x radius
• area of circle ? r2
• astronomical unit 1 AU 150 x 106 km
  average distance from Earth to Sun
• speed of light 300,000 km/sec
• light year 1 LY distance light travels in one
  year
• distance speed x time

4
Definitions and Facts

• Age of the universe 12-17 billion years old
• Measuring distances
• parallax
• triangulation
• angles, baseline
• angular measurement
• Stars and constellations
• Polaris is North Star, marks the position in
  the sky of Earths rotation axis.
• The Big Dipper is located in Ursa Major.
• Orion is a prominent constellation in the winter
  sky.
• Sirius is the brightest star in the sky.
• Celestial Sphere
• North celestial pole, celestial equator, meridian
• ecliptic, zodiac, equinoxes, solstices
• right ascension, declination
• altitude, azimuth, horizon, zenith

5

• Motion of the Earth
• rotation
• cause of day/night
• from WEST to EAST which causes objects to rise in
  EAST and set in WEST
• describe daily motion of stars, Sun, and Moon
  across sky at different latitudes
• orbital motion
• seasonal variation of constellations
• seasons
• rotational axis tilted at 23.5o to ecliptic
• seasonal variation of Suns rising/setting/noon-ti
  me position

6

• Motion of the Moon
• orbital motion
• in eastward direction around Earth with angular
  speed of 0.5o per hour
• lunar phases
• new, full, first quarter, last quarter, gibbous
  and crescent (waxing/waning)
• relationship between lunar phase and
  rising/setting time
• rotation
• rotates once per orbit about Earth synchronous
  rotation
• always see same face of Moon from Earth

7
The Sky from Denton 33.5o N

• North Celestial Pole is 33.5o above northern
  horizon.
• Celestial Equator is 56.5o above southern
  horizon.
• Circumpolar stars lie within 33.5o of North
  Celestial Pole.
• Rising Setting stars are visible from 33.5o
  away from South Celestial Pole.
• Stars within 33.5o of South Celestial Pole are
  never visible from Denton.

8
The Earths Rotation

• The Earth's west to east rotation causes the
  celestial sphere to appear to rotate from east to
  west in 24 hours.
• LOOKING SOUTH
• The Sun, Moon, planets, and stars appear to rise
  in the east, cross the meridian due south, and
  set toward the west.
• Celestial objects are said to transit when the
  cross the celestial meridian in the southern sky.
  This is when they are highest in the sky.
• LOOKING NORTH
• The stars appear to circle around the North
  Celestial Pole (near Polaris) once in 24 hours.
  
• Stars within the angle of the observer's latitude
  away from the North Celestial Pole never rise or
  set. They are always above the horizon
  (circumpolar stars).

9
The Effects of Precession

• Causes the pole star to change.
• Thuban (in Draco) was the pole star in 3,000
  B.C..
• Polaris (in Ursa Minor) is the pole star now.
• Vega (in Lyra) will be the pole star in 14,000
  A.D.
• Causes intersection point of ecliptic and
  celestial equator to shift.
• "Age of Aries" occurred 2,000 years ago.
• "Age of Pisces" is now.
• "Age of Aquarius" will begin about 400 years from
  now.

10
The Earths Orbital Motion

• The Earths orbital motion causes
• the apparent eastward motion of the Sun along the
  ecliptic of about 1o per day.
• the annual motion of the Sun through the 13
  zodiac constellations.
• the seasonal visibility of stars and
  constellations.
• The tilt of Earths rotation axis by 23.5o causes
• tilt of the ecliptic with respect to the
  celestial equator.
• the Sun's declination to change during the year.
• seasonal variations in the altitude of the midday
  Sun, length of day night, and rising
  setting directions of the Sun.

11
Eclipses

• The Moon's orbit is inclined about 5o to the
  ecliptic. That's why there are not eclipses
  every month.
• In order for an eclipse to occur, the Earth,
  Moon, and Sun must be nearly perfectly aligned.
• All eclipses occur when the Moon crosses the
  ecliptic.
• Solar eclipses are possible only at the New Moon
  phase, when the Moon is crossing the Earth's
  orbital plane (ecliptic).
• Lunar eclipses are possible only at Full Moon
  phase, when the Moon is crossing the ecliptic.

12
Solar and Lunar Eclipses

• Solar Eclipses
• Earth moves into the Moon's shadow.
• Occur only the the New Moon phase.
• Visible only over a narrow path across the Earth.
  
• Can be total, annular, or partial.
• Total solar eclipses are possible because the
  angular size of the Sun and Moon are very nearly
  equal.
• Lunar Eclipses
• Moon moves into Earth's shadow.
• Occur only at the Full Moon phase.
• Are visible over the entire night side of the
  Earth.
• Can be total, partial, or penumbral.
• A total lunar eclipse does not get completely
  black, because some light from the Sun is bent
  around the Earth by the Earth's atmosphere.

13

• Planetary Motions and Configurations
• all planets orbit EASTWARD around the Sun
• the further from Sun, the slower the angular
  speed of the planet in orbit
• describe cause of retrograde motion, observed
  planetary phases
• define configurations
• inferior planets
• conjunction
• inferior
• superior
• maximum elongation
• superior planets
• opposition,
• conjunction,
• quadrature

14

• Planetary Motion and Models of the Solar System
• retrograde motion
• models
• geocentric
• epicycles and deferents
• heliocentric
• historical contributions to understanding of
  universe
• Aristotle
• Aristarchus
• Hipparchus
• Ptolemy
• Copernicus
• Galileo
• Brahe
• Kepler
• Newton

15

• Keplers 3 Laws of Planetary Motion
• 1st Law law of ellipses
• 2nd Law law of equal areas
• 3rd Law harmonic law (P2? a3)
• Ellipses and orbits
• eccentricity, semi-major axis, aphelion,
  perihelion
• Newtons Laws of Motion and the Law of Gravity
• 1st Law law of inertia
• 2nd Law force law (Fma)
• 3rd Law action-reaction law
• Law of Gravity gravitational force between two
  objects is proportional to the product
  of the mass of each object divided by the
  distance between their centers squared.
• Concepts
• Acceleration due to gravity same on objects of
  different mass, but force of gravity on
  each object is different.
• Force exerted on pebble by Earth is the same
  size, but opposite direction as force exerted on
  Earth by pebble.
• Why does the Moon orbit the Earth when the
  Earths gravity is pulling the Moon down toward
  Earth?

16

• Forces and Motion
• Definitions and Examples
• mass,
• inertia
• speed
• velocity
• acceleration
• force
• gravity
• weight

17

• Waves and Wave Motion
• definitions
• wavelength distance between crests of a wave
• amplitude intensity or height of a wave
• frequency number of waves per second
• period time between successive wave crests
  (1/frequency)
• wave speed frequency x wavelength
• transverse and longitudinal waves
• properties of waves
• reflection
• refraction
• dispersion
• diffraction
• interference constructive, destructive
• superposition
• Doppler effect

18

• Electromagnetic Spectrum
• electromagnetic waves
• created by acceleration of charged particles
• transverse wave
• transmit energy through space
• need NO medium to propagate
• all wavelengths travel at same speed in a vacuum,
  c 3x105 km/s
• components in order of increasing wavelength
• gamma rays, X-rays, ultraviolet light, visible
  light, infrared light, radio waves
• relationship between energy, frequency, and
  wavelength of light
• E ? f or E ? 1/?
• high energy radiation high frequency, small
  wavelengths, blue color
• low energy radiation low frequency, large
  wavelengths, red color
• Kirchoffs Laws
• relate patterns within an observed spectrum to
  the object producing the spectrum
• understand how features are produced
• continuous spectrum
• emission spectrum
• absorption spectrum

19

• Atomic Structure
• protons, electrons, neutrons
• Bohr model of atom
• solar system model with quantized electron
  energy levels
• ground state, excited states, ionization
• transitions between states
• electron excited by absorbing photon with right
  energy
• electron de-excited by emitting a photon
• relationship between electron energy levels and
  atomic spectra
• each element has unique emission/absorption
  spectrum
• properties of objects determined by studying
  spectra they produce
• temperature, motions, composition, etc.
• sources of spectral line broadening

20
Example Questions
1 According to Newton, if the mass of the Earth
tripled, your weight would _________. A.    
remain the same B.     be one half of its
current value C.     be one third of its current
value D.     Three times its current
value E.      quadruple its current value
The distance between successive wave crests is
defined as the _________ of that wave. A.    
frequency B.     amplitude C.     period D.    
wavelength E.      wave speed

• 1.   A comet orbiting the Sun has an aphelion
  distance of 90 AU and a perihelion distance of 70
  AU. The semi-major axis of the asteroid's
• orbit is ________.
• 10 AU
• 20 AU
• 80 AU
• 160 AU
• 714 AU

21
Example Questions
If the same net force is applied to two objects,
one with a mass of 10-kg and the other with a
mass of 5-kg, which of the following statements
is TRUE? A.    A. The 10-kg mass will have twice
the acceleration of the 5-kg mass. B.    B. The
5-kg mass will have twice the acceleration of the
10-kg mass. C.    C. Both objects will have the
same acceleration, since the force determines the
acceleration.

• What is emitted from an atom when one of its
  electrons makes a transition from a higher energy
  state to a lower energy state?
• A photon.
• A neutron.
• An electron.
• A proton.
• Nothing, the atom becomes smaller.