NANCY

4 for Nancy

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.

· 2.

· 3.

· 4.

· emitted in small, discrete packets or quanta of energy whose individual

· energies were inversely proportional to the wavelength of the light.

· made up of small, discrete packets or quanta of energy whose individual

· energies were all the same, independent of wavelength.

· emitted as continuous waves whose wavelength was inversely

· proportional to the temperature of the object.

· 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.

· 2.

· 3.

· 4.

· inside meteorites that had come from outer space.

· on the Sun, from the emitted spectrum from its upper atmosphere.

· in rocks containing radioactively decaying elements such as uranium.

· 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.

· 2.

· 3.

· 4.

· molecule.

· excited atom.

· isotope.

· 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.

· 2.

· 3.

· 4.

· CCD array

· interferometer

· diffraction grating

· prism

·  
1 points

Question 6

·   To a physicist, a blackbody is defined as an object that   Answer

· 1.

· 2.

· 3.

· 4.

· reflects all radiation that falls on it, never heating up and always appearing black.

· always emits the same spectrum of light, whatever its temperature.

· absorbs all radiation that falls on it.

· 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.

· 2.

· 4.

· 3.

· 2.

· 4.

· 296.5.

· 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.

· 2.

· 3.

· 4.

· 3.8 × 10–19 joules

· 3.0 × 10–19 joules

· 4.5 × 10–19 joules

· 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.

· 2.

· 3.

· 4.

· the low-density atmosphere of the star emitting light in all directions.

· the hot, dense, opaque gas of the star’s surface.

· only the part of the low-density atmosphere that is between Earth

· and the surface of the star.

· 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.

· 2.

· 3.

· 4.

· each different element has a characteristic line spectrum.

· they are the only light bright enough to be seen over long distances.

· only stars produce bright line spectra.

· they can be observed through a diffraction grating.

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