Post-17.1: What event(s) are occurring in the atoms that
result in the absorption lines?
a. Electrons are transiting from higher to lower
energy levels.
b. Electrons are transiting from lower to higher
energy levels.
c. The nuclei of the atoms are radiating gamma
rays.
d. The atoms are all being ionized.
©2014 W. W. Norton & Company, Inc.
12
Post-17.1: What event(s) are occurring in the atoms that
result in the absorption lines?
a. Electrons are transiting from higher to lower
energy levels.
b. Electrons are transiting from lower to higher
energy levels.
c. The nuclei of the atoms are radiating gamma
rays.
d. The atoms are all being ionized.
©2014 W. W. Norton & Company, Inc.
13
Post-17.2: True or False: Star I has weak hydrogen lines
because all of the hydrogen has been fused to helium.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
14
Post-17.2: True or False: Star I has weak hydrogen lines
because all of the hydrogen has been fused to helium.
a. true
b.false
©2014 W. W. Norton & Company, Inc.
15
Post-17.3: True or False: Star I has weak hydrogen lines
because while there are photons energetic enough to
energize the electrons to the second energy level, most
of the hydrogen atoms are ionized.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
16
Post-17.3: True or False: Star I has weak hydrogen lines
because while there are photons energetic enough to
energize the electrons to the second energy level, most
of the hydrogen atoms are ionized.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
17
Post-17.4: True or False: Star VI has weak hydrogen
lines because most of its hydrogen electrons remain in
the ground state.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
18
Post-17.4: True or False: Star VI has weak hydrogen
lines because most of its hydrogen electrons remain in
the ground state.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
19
Post-17.5: True or False: Star VI has weak hydrogen
lines because there are not enough high-energy UV
photons available to energize the electrons to the second
energy level.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
20
Post-17.5: True or False: Star VI has weak hydrogen
lines because there are not enough high-energy UV
photons available to energize the electrons to the second
energy level.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
21
Post-17.6: True or False: Star II has very strong
hydrogen lines because it is a very old star and is 75
percent hydrogen and 25 percent helium.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
22
Post-17.6: True or False: Star II has very strong
hydrogen lines because it is a very old star and is 75
percent hydrogen and 25 percent helium.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
23
Post-17.7: True or False: Star II has very strong
hydrogen lines because its surface temperature is hot
enough to excite hydrogen electrons to the second
energy level but not hot enough to ionize the atoms.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
24
Post-17.7: True or False: Star II has very strong
hydrogen lines because its surface temperature is hot
enough to excite hydrogen electrons to the second
energy level but not hot enough to ionize the atoms.
a. true
b. false
©2014 W. W. Norton & Company, Inc.
25
This concludes Activity 17: Spectral
Classification of Stars
©2014 W. W. Norton & Company, Inc.
26