Emission lines are produced by ____
a. atoms that become ionized
b. electrons that transfer from a high energy level to a low energy level
c. electrons that transfer from a low energy level to a high energy level
d. the intensity of agitation of atoms in a hot gas
e. the motion of an object toward or away from the observer
b
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A 6.0-kg object is falling downward with an acceleration of 3.27 m/s2 . Of the following values, which is nearest to the drag force on the object?
a. 3.3 N b. 65 N c. 20 N d. 39 N
The Milky Way is part of I. a poor cluster. II. a rich cluster. III. the Virgo Cluster. IV. the Local Group
a. I and III b. I and IV c. II and III d. II and IV e. just III
A conducting hollow cylinder (inner radius = a, outer radius = b) carries a current of 40 A that is uniformly distributed over the cross section of the conductor. If a = 3.0 mm and b = 6.0 mm, what is the magnitude of the (line) integral 
around a circular path (radius = 5.0 mm) centered on the axis of the cylinder and in a plane perpendicular to that axis?
A. 50 ?T ? m B. 30 ?T ? m C. 22 ?T ? m D. 37 ?T ? m E. 47 ?T ? m
What happens to the core of a star after it ejects a planetary nebula?
A) It contracts from a protostar to a main-sequence star. B) It becomes a neutron star. C) It becomes a white dwarf. D) It breaks apart in a violent explosion. E) None of the above