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ASTA02H3 Study Guide - Midterm Guide: Occultation, Galactic Center, Semi-Major And Semi-Minor Axes

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Diana Valencia
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ASTA02 Lecture 01 Notes
It is electromagnetic radiation
Can be treated as:
o Wave: regular fluctuation in the intensity of electric and magnetic fields
Travels through vacuum at speed of light (c=300,000 km/s)
Does not need a medium to spread
o Particle: photons are massless particles that carry energy at speed of light
Distinct energy value proportional to frequency
  (f: frequency, h: planck constant)
Electromagnetic spectrum is a sequence of photon energies running from low to high
Luminosity (L) is the measure of total energy output
o Independent of distance
o Inherited property
o Measured in energy/sec (J/sec)
Brightness (B) is the energy flux/number of photons per time per receiver area
o Dependent on distance
o Measured in flux units: energy/sec/area (J/sec/m2)
 
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ASTA02 Lecture 02 Notes
Fundamental Forces of Nature
All interactions in nature are governed by four fundamental forces:
o Gravitational force: gravitation binds masses over long distances
Weakest force
Mediates orbital motions
Rules on largest scale
(inverse-square law)
o Weak nuclear force: responsible for radioactivity
Second weakest force
Mediates radioactivity
o Electromagnetic force: acts between charged particles
Second strongest force
Long-range, inverse-square law force
Binds electrons + protons atoms molecules
Mediates chemical reactions
Rules on atomic scales
o Strong nuclear force: binds quarks protons + neutrons nuclei
Strongest force
Mediates nuclear reactions
Rules on nuclear scale
Matter: Atoms
Found primarily in the form of atoms
Range of ordinary matter
o Fundamental particles (quarks and leptons)
o Subatomic particles (protons, neutrons, and electrons)
o Single atom (H, He, Fe, etc.)
o Simple molecules (O2, H2O)
o Macromolecules (DNA, complex polymers)
o Macroscopic objects (rocks, people, planets, etc.)
Atoms are mostly empty space (1/1015 is occupied)
o Cloud of electrons (e-) orbiting the nucleus
o Nucleus contains protons (p+) and neutrons (n0)
o Volume is threaded by electromagnetic fields
Isotopes are elements with same # of protons, different # of neutrons
o Isotopes of given element are chemically identical but have different mass
Light and matter interact in many ways:
o Matter can transmit light (glass, water)
o Matter can reflect light
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o Matter can gain energy by absorbing light (internal energy)
o Matter can lose energy by emitting light (internal energy)
Temperature is measure of internal energy content of an object
o Solids: higher temps, higher vibrational energy per atom/molecule
o Gases: higher temps, higher kinetic energy per atom/molecule
o Kelvin Temperature scale is absolute temperature
Proportional to amount of internal energy
K = C + 273
0 K = absolute zero
273 K = pure water freezes
373 K = pure water boils
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