ASTRONOMY 122                  	
April 16, 2013                	


1.	When visible light passes through a prism of glass, which
        wavelengths of light are refracted most by the glass?

		c.	the shorter wavelengths (blue)

2. 	The best shape for the cross-section of a large astronomical mirror 
        in order to produce the sharpest images of very distant objects is

		d.	a parabolic shape

3.	Where are new stars born?

		d.	within dark clouds in interstellar space

4.	Which of the following types of telescope will suffer from chromatic 
        aberration unless expensive measures are taken to avoid it?

		c.	refracting telescope

5. 	Chromatic aberration occurs in a telescope when

		a.	the different colors of light come to different focal points

6.	Astronomy from space vehicles is particularly useful because
		
		a.	the telescope is above the Earth's absorbing and distorting atmosphere
			and can measure radiation over a very wide wavelength range.

7.	On the absolute scale of temperature (in degrees Kelvin, or Kelvins), 
        the zero of the scale corresponds to 

		d.	the temperature at which the motion of atoms and molecules ceases.

8.	On the absolute Kelvin temperature scale, the temperature of freezing water is about

		c.	+273 degrees 

9. 	As a new star evolves from cool dust and gas to a hot star, the peak wavelength 
        of its spectrum of electromagnetic radiation will

		b.	change from the infrared to the visible wavelengths

10.	Which of the following are made of "star dust"?

		a.	spiders
		b.	buildings
		c.	the Sun
---->		d.	all of the above.

11.	Increasing the diameter of the mirror or lens of a telescope will:

		b. 	improve its resolution

12.	Refracting telescopes are limited because:

		b.	lenses bend different colors of light different amounts

13.	Comparing refracting and reflecting telescopes:

		b.	it is practical to build larger reflecting telescopes

14.	Which of the following types of the electromagnetic radiation could provide 
        the best resolution in the same size instrument?

		d.	visible light 

15.	The Doppler Effect is used by astronomers to determine:

		d.	radial speeds of stars

16. 	A star whose surface temperature is 100,000 K will emit a spectrum whose peak wavelength is 

		c.	at ultraviolet wavelengths

17.	A primary value of radio astronomy is
	
		d.	radio waves pass right through dust

18.	The early workers in spectroscopy (including Kirchhoff with laboratory spectra) 
        discovered which very significant fact about the spectra produced by hot gases, 
        such as elements heated in a flame.

		c.	each chemical element produces its own characteristic pattern of spectral
			lines.

19.	Atoms in a hot gas emit a spectrum, which is

		c.	a series of specific colors ("lines"), unique to the type of atom,
			but fixed in color when gas temperature changes

20.	The specific colors of light ("lines") emitted by an atom in a hot thin gas 
        (e.g. in a tube in a laboratory or a gas cloud in space) are caused by

		d.	electrons jumping to lower energy levels, losing energy as they do so

21.	If light from a hot, dense star passes through a cool cloud of gas 

		a.	only specific wavelengths of light ("absorption lines") will be removed 
                        from the spectrum

22.	An atom is now known to consist of

		b. 	a small, massive, electrically charged core ("nucleus") with electrons
			surrounding it

23.	A spectrum consisting of many dark lines superimposed on a continuous spectrum is 

		c. 	an absorption-line spectrum

24. 	Ionization of an atom occurs when

		a.	an electron is removed from the atom

25.	Suppose the spectrum of a solar-type star shows an equivalent set of dark 
        absorption lines, but with one exception.   Every line appears at a slightly 
        longer wavelength, shifted towards the red end of the spectrum.  What conclusion 
        can be drawn from this observation?   (Hint:  recall the Doppler effect)

		c.	the star is moving rapidly away from the Earth

26.	Stars that are just being formed are best observed by

		d.	radio waves

27.	When light from the concave primary mirror of a telescope is reflected by a 
        small secondary mirror through a hole in the primary to its focus, this is called the

		d.	Cassegrain focus

28.	Who was the first astronomer to build and use a telescope to observe the night sky?

		a. 	Galileo

29. 	The reflecting astronomical telescope with an eyepiece at the side is named for?

		b.	Newton

30.	The Helium atom is composed of

		d. 	two electrons and a nucleus of two protons and two neutrons

31.	Hans Bethe and other physicists explained the source of the Sun's energy as

		c.	the fusion of atomic nuclei

32.	Choose the correct order of electromagnetic radiations, from shortest to longest wavelength

		b.	UV, visible, IR, radio

33.	What is the one fundamental difference between x-rays and radio waves?
	
		c.	their wavelengths are very different

34.	Refraction is

		d. 	the bending of light as it crosses the boundary from one transparent
			material to another (such as a lens)

35.	What happens when a beam of white light (containing all colors) is passed through a 
        prism of glass?

		d. 	different colors are refracted at different angles to produce a spectrum

36.	The light-gathering power of a telescope is related directly to 

		a. 	the area of its primary mirror or lens

37. 	Compared with the 100-inch diameter Mount Wilson telescope, the 200-inch diameter 
        Mount Palomar telescope has a greater light-gathering power, by a factor of

		d.	4

38. 	The major cause of blurring and unsharp images of objects observed through very large 
        telescopes, at the extreme limit of magnification, is

		b.	air turbulence in the Earth's atmosphere

39.	What is the main reason for combining many radio telescopes together into an 
        interferometer with large distances between telescopes?

		b. 	to obtain much sharper images of sources

40.	The main reason for carrying a telescope and scientific equipment in an aircraft in 
        order to carry out infrared astronomy is

		c.	to avoid the absorbing effects of water vapor upon IR radiation

41. 	Given that a 6000 K surface emits radiation ("blackbody theory") with a peak 
        wavelength of 0.48 microns

		d.	a 12000 K surface has a peak at 0.24 microns

42.	Suppose star A has a surface temperature of 6000 K and star B has a surface temperature 
        of 12000 K.  Compare the energy emitted per surface area of each star.

		c.	star B will emit sixteen times star A

43. 	Parallax can be used to determine star distances for: 

		a.	stars relatively close to the sun

44. 	In understanding stars, the Bohr atom is useful for the following purpose(s):

		b.	it helps us understand the spectral lines

45.	Radio waves travel through space at what speed?

		c.	at the speed of light, 300,000 km/sec

46.	The Doppler Effect is the change in the wavelength of light caused by the source

		d.	moving with respect to the observer

47.	The peak wavelength in the spectrum of light from a star can be used to determine its

		b.	surface temperature

48.	What special event was observed in the Large Magellanic Cloud in 1987?

		c.	first supernova visible on Earth to the naked eye in 400 years

49. 	The two windows of the atmosphere are

		b. 	the optical window and the radio window

50.	What type of radiation has wavelengths greater than 100 microns?

		c.	radio waves

51.	What type of radiation has wavelengths in the range of 0.7 microns to 100 microns

		a.	visible light
		b.	gamma-rays
		c.	radio waves
---->		d.	none of the above

         (NOTE ADDED - it is infrared radiation)

52. 	The typical wavelength of visible light is

		b.	0.5 microns

53.	What is the name of the large telescope launched from the Space Shuttle in 1990?

		b.	The Hubble Space Telescope

54.	How many light years in one parsec?

		c.	about 3.3

55.	Star A appears to have the same brightness through a red and blue filter.  
        Star B appears brighter in the red than in the blue.  Star C appears 
        brighter in the blue than in the red.  Rank these stars in order of increasing 
        surface temperature.

		a.	B, A, C

56.	Electronic detectors often used to record telescopic images are

		c.	CCDs

57.	What new development in telescopes are bringing striking improvements in 
        ground-based optical telescopes?

		c.	active and adaptive optics

58.	Light with a wavelength of 400 nm (or 0.4 microns) is perceived to be

		d.	violet

59.	How many more years will the Sun shine (approximately)?

		c.	5 billion years

60.	Which photon has the highest energy?

		c.	gamma-ray

61.	An advantage of a visible light telescope is

		a.	the Earthís atmosphere is transparent to visible light

62.	The best wavelength for penetrating dusty regions of interstellar space, and detecting
	otherwise hidden objects is

		c.	radio waves

63.     The Big Bang mostly created which elements?

 		b.	hydrogen and helium

64.	The Earthís atmosphere is opaque to

		a.	gamma-rays
		b.	X-rays
		c.	ultraviolet radiation
---->		d.	all of the above

65.	The Earth's turbulent atmosphere will smear point like images of stars into ďseeing disks

		c.	a few arc seconds in diameter

66.	What is the approximate frequency of visible light?

		d.	6 x 1014 Hz

67.	What is the approximate energy carried by a photon of visible light

		d.	4 x 10-19 Joules

68.	Emission lines from molecules result from

		a.	electron orbital changes
		b.	changes in the vibrational state of the molecule
		c.	changes in the rotational state of the molecule
---->		d.	all of the above

69.	A photon of light is emitted from an atom
		
		b.	when an electron drops from an energy state to a lower energy state

70.	The relationship between energy (E) and the frequency of a photon (f) is

		a.	E = hf

71.	A photon of wavelength 10 micro-meters is considered

		d.	infrared radiation

72.	A spectroscope (or spectrograph) is

		d.	an optical device that records a spectrum

73.	Different elements can be distinguished by their emission spectrum in that

		c.	they each produce different specific emission line wavelengths

74.	The width of an emission line can be broadened through

		a.	thermal broadening
		b.	rotational broadening
		c.	collisional broadening
--->		d.	all of the above

75.	The temperature of a star can be inferred from

		a.	the peak of the continuous spectrum of the star
		b.	the width of the absorption lines in the starís spectrum
		c.	the specific lines that are present in the starís absorption spectrum
--->		d.	all of the above

76.	Astronomers analyze starlight to determine a starís
	
		a.	temperature
		b.	composition
		c.	motion
---->		d.	all of the above

77.	Compared with slowly rotating stars, the fastest spinning stars have absorption lines 
        that are

		b.	broad and fuzzy

78.	Compared with a complex atom like neon, a simple atom such as hydrogen has

		b.	fewer excited states

79.	Light behaves 
	
		c.	sometimes as a wave, and sometimes as a particle

80.	The Big Bang occurred

		c.	about 14 billion years ago

81.	The distance to the closest star beyond the Sun is about

		c.	4 light-years

82.	How is a parsec defined?

		a.	the distance which has a 1 arcsecond parallax

83.	What process has created most of the heavier elements (beyond hydrogen and helium) 
        in the Universe?

		a.	nuclear fusion within stars

84.	The resolution of a typical radio astronomy telescope for 1 meter wavelength is about

       	c.	10,000 arc-seconds

86.	What type of electromagnetic radiation is made of photons with the lowest energy?	

	Radio waves

87.	What color of visible light has the shortest wavelength?	

	Violet 

88.	What molecule in the atmosphere is a strong absorber of infrared radiation?

	Water (or H20)

89.	The diameter of the primary mirror of the Hubble Space Telescope is 2.4 meters. 
        Calculate the angular resolution for visible light.
	(Hint: ang. res. (in arc-secs) = 0.25  x  wavelength(microns)  /   diameter(meters)  )

	ang. res = 0.25 x 0.5 / 2.4   arc-sec = 0.05 arc-sec

90.	What was the first astronomical radio source discovered by Karl Jansky?

	The Center of the Milky Way Galaxy

91.	Calculate the distance of one light year in kilometers, beginning from the speed of 
        light (show the calculation). 

	One light-year = the speed of light multiplied by the length of a year

			= 300,000 km/sec  x 60 sec/min  x 60 min/hour x 24 hours/day x 365 days

			= 9.5 x 1012 kilometers


92.	What effect causes the colors of a moving object to be shifted to red or blue .

	Doppler Effect

93.	What is the brightest star in the evening sky?

	Sirius