http://www.astronomynotes.com/light/discretc.gif
Suppose two observers look at the spectrum of a
cloud of gas in a laboratory; the first reports seeing
emission lines and the second reports absorption
lines. Explain.
1) Only the first observer sees the gas against a
hot background
2) Only the second observer sees the gas against a
hot background.
3) One observer is moving rapidly relative to the
other.
4) The atoms in the gas are forming molecules.
http://upload.wikimedia.org/wikipedia/commons/thumb/b/b2/Hydrogen_transitions.svg/2000px-Hydrogen_transitions.svg.png
656 nm
486 nm
434 nm
410 nm
656 nm: red-orange
486 nm: blue
434 nm: indigo
410 nm: violet
http://www.daviddarling.info/images/hydrogen_spectrum.gif
Atoms of different elements have unique
spectral lines because each element
1) has atoms of a unique color.
2) has a unique set of neutrons.
3) has a unique set of electron orbits.
4) has unique photons.
http://webmineral.com/help/FlameTest.shtml
Atoms have particular associated spectral lines
because
1) electrons have only certain allowed orbits.
2) light consists of waves.
3) light waves can show the Doppler effect.
4) speed of light in a vacuum is a constant.
In the Sun, the transition from level 4 to level 2
of hydrogen produces photons with a
wavelength of 486.1nm. In a star twice as hot as
the Sun, this transition would produce photons
with
1) half that wavelength.
2) the same wavelength.
3) twice that wavelength.
4) four times that wavelength.
Here is the spectrum of a mystery star: Which elements are present?
1.
2.
3.
4.
Calcium only
Calcium and hydrogen
Magnesium and calcium
Calcium, hydrogen, and magnesium
Here is the spectrum of a mystery star: Which elements are present?
1.
2.
3.
4.
Calcium only
Calcium and hydrogen
Magnesium and hydrogen
Calcium, hydrogen, and magnesium
Decoding Cosmic Spectra
http://www.pbs.org/wgbh/nova/space/decoding-cosmic-spectra.html
Here is the spectrum of a mystery star: Which elements are present?
1.
2.
3.
4.
Calcium, hydrogen, and magnesium
Calcium and hydrogen
Magnesium and hydrogen
All of them
http://abyss.uoregon.edu/~js/hc209/lectures/lec09.html
http://jersey.uoregon.edu/prf/
THE SPECTRAL SEQUENCE
Class
O
B
A
F
G
K
M
L
T
Spectrum
ionized and neutral
helium, weakened
hydrogen
neutral helium,
stronger hydrogen
strong hydrogen,
ionized metals
weaker hydrogen,
ionized metals
still weaker hydrogen,
ionized and neutral
metals
weak hydrogen,
neutral metals
little or no hydrogen,
neutral metals,
molecules
no hydrogen, metallic
hydrides, alkalai
metals
methane bands
Color
Temperature
bluish
31,500-49,000 K
blue-white
10,000-31,500 K
white
7500-10,000 K
yellowish white
6000-7500 K
yellowish
5300-6000 K
orange
3800-5300 K
reddish
2100-3800 K
red-infrared
1200-2100 K
infrared
under 1200 K
O
B
A
F
G
K
M
L
T
Origins: Decoding Spectra of Light from Distant Galaxies
Origins Hour 4, Back to the Beginning, Chapter 6
http://www.pbs.org/wgbh/nova/programs/ht/qt/3114_06.html