PHYSICS 1306

EXAM I

Form 1                                                                                                              Dr. Pinsky

Spring 2004

Your seat number is printed on your answer sheet

Sit ONLY in the seat corresponding to that number!

 

This is a CLOSED BOOK exam.  You may use a calculator, however you may not have any information stored in any user changeable memory prior to the beginning of the exam for any calculator that you use.  Keep your eyes on your own paper at all times.  THERE MAY BE MORE THAN ONE CORRECT ANSWER PER QUESTION, OR THERE MAY BE NO CORRECT ANSWERS FOR A QUESTION.  Mark all correct answers.  Grading will be RIGHT MINUS WRONG (answer by answer, not question by question).  DO  NOT  GUESS ! ! !

 

 

 1.       Concerning stellar motion:

 

              a.     radial motion measures the speed of approach or recession with respect to the observer.

              b.    It is entirely possible for two different stars to have the same proper motion.

c.     proper motion refers to the apparent motion of a star in km per second with respect to the background sky.

              d.    the antapex is the point in the sky from which we appear to be coming.

              e.    a starÕs ŌSpaceĶ motion is its actual true vector velocity motion with respect to the Sun.

 

 

 2.       Which of the following indicate the source is receding (NOTE:  l is a wavelength, n is a frequency, L means "laboratory", O means "observed", and c = 3 x 108 m/sec.):

 

              a.     lO = 499 nm and lL = 498 nm

              b.    nO = 29.8 MHz and nL = 28.9 MHz

              c.     lO = 230 nm and lL = 220 cm

              d.    nO = 10 kHz and nL = 400 MHz

              e.    nO = 300 kHz and lL = 1 m

 

 

 3.       Which of the following stars is cooler than a G2 star:

 

              a.     O5                                         

              b.    M9                       

              c.     G3                        

              d.    G1                                          

              e.    K1                                          

 

 4.       For star A we have:  TA = 6,000K, dist. = 10 pc, dia. = 4 x105 km

              For star B we have:  TB = 12,000K, dist. = 1000 pc, dia. = 105 km

 

              a.     star A has an apparent magnitude greater than star B.

              b.    star A will appear bluer than star B.

              c.     star A the same absolute magnitude as star B.

              d.    for star A the absolute magnitude = apparent magnitude.

              e.    star B has a brighter surface than star A (per m2).

 

 


 5.       Hipparchus:

 

              a.     was the first to prove that the earth rotated on its axis.

              b.    is considered to be the greatest observational astronomer in antiquity.

              c.     invented the Stellar Magnitude system we use today.

              d.    was the first person to suggest the earth revolved about the sun.

              e.    was first to suggest the Milky Way was made of stars.

 

 6.       The Greeks:

 

              a.     founded the first universities.

              b.    built Stonehenge to observe the seasons.

              c.     measured the earth's diameter.

              d.    measured the actual distance to the sun.

              e.    were the primary source of planetary position data used by Copernicus.

 

 7.       All Atoms:

 

              a.     of normal matter each have at least one proton in the nucleus.

              b.    typically absorb light when electrons fall from one energy level to a vacancy in a lower level.

              c.     are about the same size as the wavelength of x-ray electromagnetic radiation.

              d.    of normal matter if electrically neutral each have at least one electron in orbit about the nucleus.

e.       Were first theorized to exist by Democritus and his teacher Lucippus.

 

 8.       Which of the following can be determined about a star by examining only the shape of a single spectral line, without knowing which line it is (i.e., where it belongs in the spectrum):

 

              a.     the chemical composition of the star.

              b.    whether or not the star has planets.

              c.     the star's mass.

              d.    if the star is rapidly rotating.

              e.    if the star has a very high surface magnetic field.

 

 9.       Eclipsing binaries:

 

              a.     only occur near the full moon.

              b.    are the only type binaries we can get mass information from.

              c.     are always spectroscopic binaries as well.

              d.    become completely dark during an eclipse.

e.       Are generally identified by the shape of their light-curves over time..

 

10.     The Doppler effect:

 

              a.     is sometimes referred to as the Zeeman Effect.

              b.    in sound, causes a shift to a lower pitch for sound emitted by an receding source.

              c.     was first discovered by Galileo.

              d.    is only measurable when the velocity of the source is >> 1/10 of the speed of light.

              e.    occurs for all wave phenomena rather than just visible light.

 

11.     Concerning Binary Stars:

 

              a.     one can always see both stars in visual binary.

              b.    are called optical if both can be seen (in a telescope), and represent true mutually orbiting stars.

              c.     in the case of both spectrum and spectroscopic binaries you must be able to resolve both stars optically from one and other to be able to tell that there are two stars present.

              d.    they obey Kepler's Laws.

              e.    are our only source of stellar mass information.

 


12.     If a particular star has a surface temperature of 6,000 K and a black body spectrum that peaks at 500 nm, the spectrum of a:

 

              a.     3,000 K star peaks at 1000 nm.

              b.    12,000 K star peaks at 250 nm.

              c.     3,000 K star peaks at 250 nm.

              d.    12,000 K star peaks at 2000 nm.

              e.    all stellar spectra peak at 500 nm because of the earth's atmosphere.

 

 

13.     Which of the following are variable stars:

 

              a.     RR Centauri  

              b.    a Lyrae                            

              c.     26 Lyrae          

              d.    AA Canis Majoris  

              e.    M31

 

 

14.     Mark the TRUE statements:

 

a.     All light may appear to move either faster or slower than in a vacuum, depending the relative speeds of the source and observer with respect to each other.

              b.    Magnetic fields can be felt only by charges that are moving with respect to the field.

              c.     Changing electric fields create magnetic fields.

              d.    Light is an oscillating and propagating gravitational wave.

              e.    Magnetic fields are created by charges only when they are moving.

 

 

15.     Issac Newton:

 

              a.     originated the 3 Laws of Planetary Motion now known as Kepler's Laws.

              b.    was the primary inspiration for Galileo.

              c.     was the first person who recognized the law of Inertia.

              d.    invented the reflecting telescope.

              e.    included the conservation of angular momentum directly as one of his  3 -Laws of Motion.

 

16.     Concerning stellar magnitudes (Mark the true statements):

 

a.     a star with an apparent magnitude of +5 would appear brighter to the eye than +15 apparent magnitude star.

b.    a difference of 10 in absolute magnitude between two stars means a luminosity difference of 10,000 times.

c.     apparent magnitude will always be a smaller algebraic number than absolute magnitude.

d.    if one knows both the absolute and apparent magnitude of a star, the starÕs distance can be calculated.

e.    if two stars have different apparent magnitudes then they must have different absolute magnitudes.

 

 

17.     A binary system has equal mass stars each with a mass 4 times that of the sun and a period of 8 years.  If the separation between them remains constant throughout the entire revolution then:

 

              a.     one cannot calculate their mutual separation distance given the data at hand.

              b.    their mutual separation is 10 AU.

              c.     their mutual separation is 8 AU.

              d.    their mutual orbits must be circles.

              e.    their mutual separation is equal to the cube root of 128 AU.


18.     Mark the TRUE statements:

 

a.     If two stars have the same luminosity they will always appear to us to have the same absolute magnitude.

b.    The bluer stars will always seem brighter in the sky than redder stars.

c.     Stars with the same spectral type and luminosity as the sun have absolute magnitudes of one by definition.

d.    Stellar parallax was first observed by Aristotle.

e.    stellar mass information is only known from measurements of binary systems.

 

 

19.     If a hypothetical planet were 2 times the mass and twice the diameter of the earth.

 

              a.     the acceleration of gravity at its surface would be 2 times that at the earth's surface

              b.    the acceleration of gravity at its surface would be one half times that at the earth's surface

              c.     the acceleration of gravity at its surface would be the same that at the earth's surface

              d.    the density of the planet would be twice as much as the EarthÕs density

              e.    the density of the planet would be one-quarter as much as the EarthÕs density.

 

20.     If two stars are the at same distance, but one has one ninth of the diameter and  three times the temperature, this hotter star is:

 

              a.     not as luminous as the cooler star.

              b.    has the same luminosity as the cooler star.

              c.     twice as luminous as the cooler star.

              d.    9 times the luminosity of the cooler star.

              e.    more luminous than the cooler star.

 

 

21.     Galileo:

 

a.     invented a reflecting telescope where the image is viewed at a right angle with respect to the observing direction.

b.    is considered the father of modern science for his reintroduction of an empirical philosophy in science.

c.     was the first person to note the precession of the earth's axis of rotation.

d.    was first to report seeing the crescent phases of Venus.

e.    discovered the 1/r2 dependence of the gravitational force.

 

 

22.     Mark the TRUE statements:

 

              a.     Mass is a vector quantity.

              b.    Angular momentum is absolutely conserved in magnitude but not in direction.

              c.     Energy is absolutely conserved.

              d.    Momentum is absolutely conserved in both magnitude and direction.

              e.    Energy is a vector quantity.

 

 

23.     Concerning the type of spectra emitted:

 

a.     one would expect a diffuse cloud of gas in space to convert an incident continuous spectrum into an absorption spectrum as light traverses it and emerges from the far side of the cloud.

b.    a black body spectrum is an emission spectrum.

c.     most stars have an absorption spectrum as seen from earth.

d.    the sun's Fraunhofer spectrum is an emission spectrum as seen from earth.

e.    all elements have different absorption spectra.


24.     Which of the following can be resolved in a visible light telescope with an objective mirror diameter of 1 m?  [Hint: First, calculate the resolution in radians, then convert that to arc secÉ]

              (NOTE:  For visible light l = 500 nm = 5 x 10-7 m, and 1"arc ~ 5 x 10-6 radians):

 

a.     a car (~ 5 m) where the telescope is in a spy satellite orbiting at an altitude of 500 km directly overhead.

              b.    the annual parallax of a star at 1 pc.

              c.     as a visual binary, two stars separated by 0.001 arc sec.

              d.    the proper motion in one year of a star moving 1.0 arc sec./year.

              e.    two stars separated by 1 pc at a distance of 109 pc.

 

25.        Concerning telescopes:

 

a.       The big advantage the Hubble Space Telescope over those on earth is its weightless environment.

b.       All telescopes used for astronomical purposes are used in the visible wavelengths.

c.       Optical telescopes are usually placed on mountaintops principally to avoid city lights.

d.       Newton was one of the first people to figure out how to make one using a mirror rather than a primary lens.

e.       Photographic Film is no longer very widely used for seeing images on large research telescopes.