Transcript Introduction to Electromagnetism

Physics of Astronomy- spring
Dr. E.J. Zita, The Evergreen State College, 29.Mar.2004
Lab II Rm 2272, [email protected], 360-867-6853
http://academic.evergreen.edu/curricular/ PhyAstro/home.htm
Outline
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Logistics and time budget
Special events & info
Review of last quarter’s content
Preview of spring quarter
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Introduction to Modern Astrophysics Ch.9
Spring weeks 1-2
Minilecture signup
Astronomy signup
Logistics and time budget
Seminar: Read, preseminar, and write (or rewrite) one paper per week.
Research: Spend 12-16 hours per week carrying out your plan, reading, and
doing calculations.
Texts, classes, and homework:
Please present in Astronomy & Cosmologies (AC) every other week
Each team minilecture once per week in Physics of Astronomy (PA)
(homework-focussed)
NEW: P&Q (Points and questions) at least once a week in PA
Total ~ 48-60 hours/week, so be sure to schedule in R&R, to stay healthy
Special events & info
Spring Science Fair at Evergreen – you will definitely present a poster of your
research there: May 28-29 (week 9)
APS-NW = American Physical Society – Northwest Section meeting
Moscow, Idaho / Pullman, WA 21-22 May (Fri.Sat end of week 8)
Do you want to go? Present a poster of your research
Deadline for registration and Abstracts: 23 April (week 4)
Calculus tutorials with Matt (details TBA)
TAs = Emily Himmelright and Jenni Walsh
Office hours: Wednesday 5-6 in fishbowl
Review of winter quarter content
Intro to Modern Astrophysics
Carroll and Ostlie = CO
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Basic astronomy 
Gravity + orbits 
Light + spectra 
Modern physics, QM 
Electromagnetism 
• Sun and Stars
• Thermal + radiation
• Cosmology
Physics and Astronomy
Physics: What fundamental, quantitative principles explain the
structure and evolution of the natural world?
Astronomy: What do we see in the sky, and how do things move and
change?
Astrophysics: How can Physics explain what Astronomy observes?
Four realms of physics
Classical Mechanics
Quantum Mechanics
(big and slow:
everyday experience)
(small: particles, waves)
Special relativity
Quantum field theory
(fast: light, fast particles)
(small and fast: quarks)
Ch.1: The Celestial Sphere
(Figures from Freedman and Kaufmann, Universe)
1.1: The Greek Tradition; Team 1: Celestial Sphere
1.2 The Copernican Revolution; Team 2: Periods; prob.1.3
1.3 Positions on the Cel.Sph.
Team 3.a: Altitude+ Azimuth (p.10-13), prob. 1.5
Team 3.b: Right Ascension and Declination (p.13-15), prob.1.4
Team 3.c: Precession and motion of the stars (p.15-19), prob.1.6
1.4 Physics and Astronomy
Ch.1: Key concepts
arclength D = d a when a is in radians
Alt-Az above, RA-Dec below
 1 1
1
   
S
 P P 
Ch.2: Celestial Mechanics
2.1 Elliptical Orbits
2.2 Newtonian Mechanics: F 
GmM
rˆ
2
r
and conservation of angular momentum
2.3 Kepler’s Laws: we derived K3 from N2: 4p2r3 = GMT2
We derived the Schwarzschild radius for a black hole;
we weighed Jupiter and the Sun using orbital satellites, and
we discovered dark matter in Galaxies from non-Keplerian
velocity curves
2.4 The Virial Theorem: E = U/2 in a central field.
Keplerian orbits: closer = faster
Spherical coordinates
Ch.3: The continuous spectrum of Light
3.1
3.2
3.3
3.4
3.5
Parallax  distance  brightness
Magnitude
Wave nature of light
Radiation
Quantization of Energy
3.6 Color (wavelength) 
temperature, power output,
absolute brightness…
Spectra tell us all this about stars:
• Color  temperature: l(m) = 3x10-3/T(K)
• Temperature  Power output per unit area: flux =
intensity of radiation = F=sT4
• Power output = Luminosity = L
• Intensity = power / area: F= L/4pR2
• Greater radiation flux  brighter star: F ~ b
• Brightness is perceived on a logarithmic scale.
Apparent magnitude difference m2-m1=Dm= 1 
brightness ratio b1/b2 = 100 1/5 = 2.512
• Absolute magnitude M is what a star would have if it
stood at a distance of d=10 pc from Earth.
Ch.5: Interaction of Light & Matter
5.1 Spectral lines
5.2 Photons
5.3 Bohr model
5.4 QM and wave-particle duality
Spectral lines tell us more about stars:
•Spectral lines  composition &
atmosphere, stellar type and age,
•Shifts in spectral lines  proper
motion, rotation, magnetic fields
(Zeeman),
• oscillations  internal structure,
internal rotation, planets…
Emission and absorption lines
text
Planck quantizes light energy: photons
• E = hc/l = hn  pc
• Interference + diffraction: light = wave
• Photoelectric effect: Light particles (photons) each
carry momentum p= hc/l
(Giancoli Ch.38)
• Maxwell’s theory + Hertz’s experiment: EM waves
Modern Physics
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Plancks’s light quanta!
explain the photoelectric effect (Einstein);
supported by Compton effect;
explain the H atom (Bohr)
with deBroglie’s matter waves
hf = Kmax + F
Bohr model
• DeBroglie: electrons as waves
• Planck: light as particles
• Derived H energies match observed spectra
Break time! then Spring syllabus:
Overview of Ch.9
Stellar Atmospheres
9.1: The radiation field
9.2: Stellar opacity
9.3: Radiative transfer
9.4: The structure of
spectral lines
Spring weeks 1-2: HW & ML
Astrophysics (Carroll & Ostlie) Ch.9
Astronomy (Freedman & Kaufmann)
19: The Nature of Stars
20: The Birth of Stars
21: Stellar Evolution
22: Deaths of stars
Physics (Giancoli) 17: Thermal
19: Heat
Mathematical Methods (Boas + Spiegel): review differentiation
& integration with Matt in QRC
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Minilecture signup for Astro & Cosmo
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Supper time … then, Seminar in Lib 4004