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ASTR 124


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why can a good blacksmith judge the temperature of a piece of heated iron by its color?
hot objects emit more black body radiation
why do hot starts look bluer than cold stars
hotter objects emit more blue
use black body radiation to explain why you can light a cig with a match but not a bonfire
difference b/w a neutral atom, and ion, and an excited atom?
-ion-atom that has lost 1+ electrons
-excited atom-move electron in atom to higher energy level
how do energy levels in an atom determine which wavelength photons it can absorb or emit?
atom drops from high to low energy level, emits photons. ?????
what spectrum would you record observing molten lava? through glasses?
continuous spectrum, w/ absorption lines caused by gases above.
why does the strength of the Balmer lines depend on the temp. of the star?
measure only absorption lines in 2nd energy level. cool stars have fewer violent collisions, excited atoms.
why does a stellar spectrum tell us about the surface layers but not the deeper layers of the star?
why do we not see TiO bands in the spectra of hot stars?
Absorption bands due to the molecule titanium dioxide (TiO). They are prominent in the spectra of K stars and M stars, which are cool enough for TiO to survive.
if no visible lines of element in star, is element not present?
star can be too hot or cold to produce certain lines of elements
if star moves directly perpendicular to a line connecting to earth, will dopler effect change its spectrum?
no, doppler effect can not be used to measure perp. lines
why would we expect star that rotates rapidly to have broad spectral lines? what else could broaden lines?
yes, motion smears spectral line. collision broadening smears spectral lines too. colliding atoms realease dif. levels of energy.
human body temp. is 310K, at what wavelength do humans radiate the most energy? what kind of radiation?
star w/ surface temp. of 20000k, what wavelength will it radiate most energy?
IR observations show that star is most intense at 2000 nm. what is temp. of star's surface?
double black body temp. by what factor will total energy radiated per second per sq. meter increase?
star w/ temp. 6000 K, other star w/ temp. 7000 K, how much more energy/second will hotter star radiate from each sq. meter of its surface?
transition A produces light w/ wavelength 500 nm. transition B involves 2x as much energy. what wavelength light does it produce?
i have no fucking clue

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