CODES USED IN THE GRADING:
Exp: The explanation is not sufficient
Incom: The answer is incomplete
EXAM 1 ANSWERS
- The atom will be ionized. The first Lyman
alpha photon will put the atom into the first excited state. I know that the second Lyman
alpha photon will ionize the atom because a Balmer limit photon puts the atom into the
last orbit from the first excited state. A Lyman alpha photon has more energy than the
Balmer limit photon because Lyman alpha is at a shorter wavelength than Balmer limit.
- The white dwarf and the main sequence
star have the same surface temperature but the main sequence star has more luminosity.
The Stefan-Boltzmann Law says that both stars have the same luminosity per unit area so
the main sequence star must have more area if it's more luminous.
- Newton's first law says that an object's
velocity is constant if no force acts. Newton's second law says that if a force acts on an
object, the velocity is changed at a rate (acceleration) which equals the force applied
divided by the object's mass.
In the up and down direction gravity is acting but we care about the sideways direction
since that's the velocity that's changing. If friction is slowing the book down (accelerating it)
then friction must be a force from Newton's Second Law.
- The Stefan-Boltzmann (S-B) Law tells us
that the luminosity per unit area depends on the star's surface temperature raised to the
fourth power. From the H-R diagram we see that O stars are much hotter than M stars.
If the two stars have the same size, then O stars will be more luminous.
- Main sequence stars obey the mass-luminosity
relationship: The higher the luminosity, the higher the mass. Main sequence O stars are
more luminous than main sequence M stars so they are more massive.
- M stars are cool and emit very few Lyman
alpha photons. In order for an H atom to absorb a Balmer series photon the atom must be
in the first excited state. It takes a Lyman alpha photon to move the electron into the first
excited state from the ground state. So M stars have their electrons sitting in the ground state.
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