Question 1
. If light from a hot, dense star passes through a cool cloud of gas
(see Figure 4-9, Comins and Kaufmann, Discovering the
Universe, 8th ed.),
Answer
.
.
.
.
. 1. only specific wavelengths of light will be removed from the spectrum.
.
. 2. the atoms of the gas cloud will add energy to the overall spectrum,
. enhancing
.
it at specific wavelengths to produce emission lines.
.
. 3. the whole spectrum will be reduced in intensity.
.
. 4. the cool gas will not affect the spectrum of the star because cool atoms
. cannot
.
absorb light.
. 1 points
Question 2
. In the revolution that overtook physics around 1900, the assumption
that Planck made in order to solve the problem concerning the
spectrum of radiation emitted by a hot blackbody was that radiation
was Answer
. . 1. emitted in small, discrete packets or quanta of energy whose individual
. energies
.
were inversely proportional to the wavelength of the light.
.
. . 2. made up of small, discrete packets or quanta of energy whose individual
. energies
.
were all the same, independent of wavelength.
.
. . 3. emitted as continuous waves whose wavelength was inversely
. proportional
.
to the temperature of the object.
.
. . 4. emitted in small, discrete packets or quanta of energy, each quantum
. having
.
an energy directly proportional to the wavelength of the light.
. 1 points
Question 3
. The element helium was first discovered and identified as a separate
element Answer
. . 1. inside meteorites that had come from outer space.
.
. . 2. on the Sun, from the emitted spectrum from its upper atmosphere.
.
. . 3. in rocks containing radioactively decaying elements such as uranium.
.
. . 4. in natural gas originating underground, from the spectrum emitted
. from
. a flame of burning natural gas.
. 1 points
Question 4
. An atom in which one or more electrons has been removed is known
as a(n) Answer
. . 1. molecule.
.
. . 2. excited atom.
.
. . 3. isotope.
.
. . 4. ion.
.
. 1 points
Question 5
. A particular spectrograph, used by an astronomer to disperse light
into its colors, contains a piece of glass that has been ruled with
thousands of closely spaced, parallel lines. What is the name of this
piece of glass? Answer
. . 1. CCD array
.
. . 2. interferometer
.
. . 3. diffraction grating
.
. . 4. prism
.
. 1 points
Question 6
. To a physicist, a blackbody is defined as an object that Answer
. . 1. reflects all radiation that falls on it, never heating up and always appearing black.
.
. . 2. always emits the same spectrum of light, whatever its temperature.
.
. . 3. absorbs all radiation that falls on it.
.
. . 4. always appears to be black, whatever its temperature.
.
. 1 points
Question 7
. A piece of iron is heated from 400 K to 800 K (127°C to 527°C).
The total energy emitted per second by this iron will increase
by a factor of
Answer
.
.
.
.
. 1. 296.5.
.
. 2. 4.
.
. 3. 2.
.
. 4. 16.
.
. 1 points
Question 8
. The visible region of the spectrum ranges in wavelength from about
400 nm to 700 nm. Which one of the following photons is NOT in the
visible range? Answer
. . 1. 3.8 × 10–19 joules
.
. . 2. 3.0 × 10–19 joules
.
. . 3. 4.5 × 10–19 joules
.
. . 4. 9.0 × 10–19 joules
.
. 1 points
Question 9
. The star P Cygni (in the constellation Cygnus, the Swan) is
surrounded by an extensive low-density atmosphere. It has a bright,
continuous spectrum with many narrow, dark absorption lines and a
few bright emission lines. The bright, continuous part of the
spectrum is produced by Answer
. . 1. the low-density atmosphere of the star emitting light in all directions.
.
. . 2. the hot, dense, opaque gas of the star's surface.
.
. . 3. only the part of the low-density atmosphere that is between Earth
. and
. the surface of the star.
.
. . 4. all parts of the star, the stellar surface, and the atmosphere, equally.
.
. 1 points
Question 10
. Spectral lines are of particular importance in astronomy because
Answer
. . 1. each different element has a characteristic line spectrum.
.
. . 2. they are the only light bright enough to be seen over long distances.
.
. . 3. only stars produce bright line spectra.
.
. . 4. they can be observed through a diffraction grating.
.