ASTR 250 FINALS CARDS QUESTIONS AND ANSWERS
#14
common proportionality between Coloumbs law and Force of gravity - correct answer
1/r^2 (q1*q2/r^2 and Gm1m2/r^2 respectively)
If Gravity is overpowered by EM forces at small scales, why does it matter? - correct
answer Gravity can only be positive, while at large scales objects are net neutral
charge, gravity dominates
fundamental properties of light - correct answer speed (c), direction, wavelength and
polarization, density/intensity
What parts of the spectrum does earth's atmosphere block and why - correct answer
Gamma, X ray and UV because their wavelengths are shorter, making them less
penetrative
diffraction limit proportionality - correct answer lambda/diameter
(theta=1.22*wavelength/diameter)
T/F any formula with Planck's constant h can be derived from classical mechanics -
correct answer False
Photoelectric effect proportionality - correct answer 1/lambda (E = hc/lambda)
The volume of an atom is mostly - correct answer Nothing/empty space
Electrons don't spiral due to Force of gravity because - correct answer Electric forces
dominate at small scales
Term for when object is opaque, uniform temperature and scatters photons as they exit
- correct answer Blackbody/BB
Wien's law - correct answer As thermal radiation increases, its wavelength peak is
defined by lambda_max = .29/T
Stefan-Boltzmann Law - correct answer f is proportional to T^4
Laws of Thermodynamics - correct answer "0th" Hot -> cold
1st Heat is a form of energy
2nd Entropy cannot decrease
3rd: absolute 0 temperature state exists
The more uniform things are distributed in space/energy the more/less microstates it
has and the higher/lower entropy it has - correct answer more, higher
, The proportional relation between Luminosity and Temperature, radius of BB - correct
answer Luminosity is proportional to Temperature^4, radius_BB^2
Lyman - correct answer n -> 1
Balmer - correct answer n -> 2
Paschen - correct answer n -> 3
Number of Random walks equation - correct answer N = 3R^2/l^2
Interstellar Medium is what % of the mass of our galaxy - correct answer 1% (just
remember its really low)
Scattering of light through absorption is called - correct answer extinction
Why does blue light and lower wavelength emissions scatter in dust - correct answer
Shortness of the wavelength means it interacts more with matter
What is an HII region - correct answer a region of hydrogen trying to recombine into its
neutral form, kept ionized by the emission of Lyman-continuum photons from the star
Stromgren Sphere - correct answer a section of HII region where the star keeps a
balance between ionization and recombination, emits in the optical band
HI regions - correct answer regions of the atomic state of hydrogen, occasionally spin
flips and emits distinctive 21 cm radio photons
Local standard of rest (LSR) - correct answer mean rotation of disk material in solar
neighborhood
Edwin Hubble's Classification Scheme - correct answer A forked diagram that classifies
Ellipticals (E0-E7, S0) and normal/barred spirals (Sa-Sc and SBa-SBc)
Winding problem - correct answer The winding of a spiral occurs too quickly, the
solution is the density wave phenomenon where slow moving objects cause a buildup
that persists even after the objects are passed.
Of all spirals: how much do each kind consist of the entire population - correct answer
Grand design(low arm count): 10% Multi-arm: 60% Barred: 30%
What information does the galactic Luminosity/Schechter function tell you - correct
answer Most galaxies are dim, while only a select few are bright
#14
common proportionality between Coloumbs law and Force of gravity - correct answer
1/r^2 (q1*q2/r^2 and Gm1m2/r^2 respectively)
If Gravity is overpowered by EM forces at small scales, why does it matter? - correct
answer Gravity can only be positive, while at large scales objects are net neutral
charge, gravity dominates
fundamental properties of light - correct answer speed (c), direction, wavelength and
polarization, density/intensity
What parts of the spectrum does earth's atmosphere block and why - correct answer
Gamma, X ray and UV because their wavelengths are shorter, making them less
penetrative
diffraction limit proportionality - correct answer lambda/diameter
(theta=1.22*wavelength/diameter)
T/F any formula with Planck's constant h can be derived from classical mechanics -
correct answer False
Photoelectric effect proportionality - correct answer 1/lambda (E = hc/lambda)
The volume of an atom is mostly - correct answer Nothing/empty space
Electrons don't spiral due to Force of gravity because - correct answer Electric forces
dominate at small scales
Term for when object is opaque, uniform temperature and scatters photons as they exit
- correct answer Blackbody/BB
Wien's law - correct answer As thermal radiation increases, its wavelength peak is
defined by lambda_max = .29/T
Stefan-Boltzmann Law - correct answer f is proportional to T^4
Laws of Thermodynamics - correct answer "0th" Hot -> cold
1st Heat is a form of energy
2nd Entropy cannot decrease
3rd: absolute 0 temperature state exists
The more uniform things are distributed in space/energy the more/less microstates it
has and the higher/lower entropy it has - correct answer more, higher
, The proportional relation between Luminosity and Temperature, radius of BB - correct
answer Luminosity is proportional to Temperature^4, radius_BB^2
Lyman - correct answer n -> 1
Balmer - correct answer n -> 2
Paschen - correct answer n -> 3
Number of Random walks equation - correct answer N = 3R^2/l^2
Interstellar Medium is what % of the mass of our galaxy - correct answer 1% (just
remember its really low)
Scattering of light through absorption is called - correct answer extinction
Why does blue light and lower wavelength emissions scatter in dust - correct answer
Shortness of the wavelength means it interacts more with matter
What is an HII region - correct answer a region of hydrogen trying to recombine into its
neutral form, kept ionized by the emission of Lyman-continuum photons from the star
Stromgren Sphere - correct answer a section of HII region where the star keeps a
balance between ionization and recombination, emits in the optical band
HI regions - correct answer regions of the atomic state of hydrogen, occasionally spin
flips and emits distinctive 21 cm radio photons
Local standard of rest (LSR) - correct answer mean rotation of disk material in solar
neighborhood
Edwin Hubble's Classification Scheme - correct answer A forked diagram that classifies
Ellipticals (E0-E7, S0) and normal/barred spirals (Sa-Sc and SBa-SBc)
Winding problem - correct answer The winding of a spiral occurs too quickly, the
solution is the density wave phenomenon where slow moving objects cause a buildup
that persists even after the objects are passed.
Of all spirals: how much do each kind consist of the entire population - correct answer
Grand design(low arm count): 10% Multi-arm: 60% Barred: 30%
What information does the galactic Luminosity/Schechter function tell you - correct
answer Most galaxies are dim, while only a select few are bright
